ON PETITION FOR REHEARING
MacKINNON, Senior Circuit Judge:
The Restaurant Corporation of America, Inc. (the “Company”) petitions for review of a decision and order of the National Labor Relations Board. The Board determined that the Company had violated section 8(a)(1) and (3) of the National Labor Relations Act, 29 U.S.C. § 158(a)(1), (3) by disparately enforcing its absolute no-solicitation rule by suspending and discharging employees Dameron and Herbekian because of their union activities. 271 N.L.R.B. 171 (1984). The Board cross-petitions for enforcement of its order. For the reasons set forth below, we grant the Board’s cross-petition to enforce its order as to Dameron and deny it as to Herbekian.1 Our colleague concurs in our opinion insofar as it upholds the Company’s suspension and discharge of Herbekian but dissents from our refusal to uphold the suspension and discharge of Dameron. Thus, the pivotal issue within the court is whether the Company disparately enforced its no-solicitation rule in discharging Dameron, who, when off-duty, made one isolated union solicitation (lasting less than five minutes) of two non-working employees seated together, while not enforcing the rule against employees who made numerous social solicitations of working employees.
I.
The Company owns and operates food service facilities in the Watergate complex in the District of Columbia, including Les Champs Restaurant, the Peacock Lounge, the Terrace Restaurant, the Espresso Cafe, a pastry shop, and a delicatessen. Approximately 230 persons, fourteen of whom are supervisory employees, are employed by the Company in the aforementioned enterprises. The Company’s food service employees are not represented by a union. Approximately thirty food service employees and three supervisory employees work in Les Champs Restaurant and the Peacock Lounge. In 1975 the Company adopted the [802]*802following absolute no-solicitation rule applicable to all employees:
Solicitation of any kind, including solicitation for clubs, organizations, political parties, charities, etc. is not permitted on working time or in customer areas. Distribution of literature of any kind is not permitted on working time or working areas. Offshift employees are not allowed on the premises.
(Joint Appendix (J.A.) 5) (emphasis in original).
In early 1981 Roxie Herbekian inquired of the Hotel and Restaurant Employees Union, Local 25, AFL-CIO, as to the possibility of finding work in a restaurant with an organized union. When told that such work was not available, Herbekian asked whether she might find work in a restaurant that had the prospect of being organized. The union advised her that an organizing campaign was underway in the Watergate facilities operated by the Company.
Herbekian obtained employment from the Company in January 1981 to work halftime as a morning room-service operator. The union organizing campaign, however, did not reach fruition. In mid-March Herbekian took on additional work for two or three days a week as a cocktail waitress in the Peacock lounge. Herbekian then spoke with thé union about an organizing effort among the thirty or so food service employees of the Company. With the approval of the union, Herbekian, sometime in May 1981, began speaking to her coworkers about organizing a union local. At this point Herbekian was speaking only with employees in the physically adjacent Les Champs Restaurant and Peacock Lounge. Herbekian testified that her solicitation ran as follows:
Generally, what I would say to them is that, in January I had attended a meeting with employees of the Terrace [Restaurant], a Union meeting. And, several of the employees there were interested in organizing. Yet, in order to continue the campaign, we would have to include people in the other restaurants and shops of the Watergate. And, are you — the individual I was speaking to — would you be interested in pursuing getting a Union?
(Hearing Transcript (Tr.) 32). At this time Herbekian had neither union authorization cards nor union literature. Herbekian testified that she spoke with twelve people on work time concerning the union campaign prior to June 2, 1981 (Tr. 70-77).
Among those solicited by Herbekian was Sherwood Dameron, a waiter at Les Champs. Dameron, Herbekian, and six other employees attended a union-sponsored meeting outside their work places on June 2, 1981 to discuss the prospect of organizing the employees of the Watergate complex. At this meeting each person received a list containing the names of fellow employees to contact about signing union authorization cards. Herbekian’s list contained five names; Dameron’s contained six (Tr. 81, 297).
Herbekian met with approximately ten people following the June 2, 1981 meeting. All of the meetings apparently occurred on work time. Herbekian testified that she met with “[ajbout ten” people following the June 2 meeting (Tr. 40), talking with nine specific employees on work time and in the workplace (Tr. 82-92). Herbekian described these meetings as follows:
I spoke to employees, and I asked employees to sign cards. And, I took those cards. I asked them to sign them, and then they gave them back to me. And, I reported to a number of people who asked me about the meeting, what had happened at the meeting.
(Tr. 40). As a result of these solicitations, Herbekian received seven signed authorization cards (Tr. 42).
Meanwhile, Sherwood Dameron spoke with seven employees about the union organizing effort. Five of the conversations took place entirely outside of work time (Tr. 297-300). Dameron spoke with Tiep Bui and Charatsri Maneepanth, cashiers at the Espresso Cafe, while Dameron was off the clock but while Bui and Maneepanth were sitting down together behind the counter, not actually working but during work time (Tr. 287, 299). Dameron gave [803]*803Bui and Maneepanth union authorization cards. He testified that Bui and Maneepanth were not busy, and that the solicitation of Bui and Maneepanth lasted a total of “P]ess than five minutes” (Tr. 287, 299).
One of Dameron's non-work time conversations was with Victor Sangster, a chefs helper at Les Champs. Richard Sultoni, a chef at Les Champs affiliated with management, thereafter asked Sangster whether he had been approached recently by anyone concerning a union. Sangster replied negatively. Sultoni asked Sangster what he thought of unions; Sangster replied that he did not know much about unions, but that he would inform Sultoni if he were approached regarding a union (Tr. 248-49). Tiep Bui, the cashier in the Espresso Cafe, was also questioned by Sultoni. Bui told Sultoni that Dameron had given her a union authorization card, but that she had left it at home (Tr. 109). Charatsri Maneepanth was questioned by Sultoni the day after receiving an authorization card from Dameron. Maneepanth named Dameron as the source of the card.
On the morning of Tuesday, June 9, 1981 Roxie Herbekian was summoned to the office of Gene Flick, the general manager of the Company’s Watergate facilities. Flick inquired whether Herbekian was aware of the Company’s no-solicitation rule. Herbekian answered that she was unaware of the rule. Flick gave Herbekian a copy of the rule and reminded her that the rule was prominently posted by the timeclock, in the employee locker room, and on the employee bulletin board in Les Champs and the Peacock Lounge. Flick then suspended Herbekian for three days pending investigation of her alleged violations of the no-solicitation rule. When Herbekian returned to work the following Monday, she was fired by Flick.
Flick called Dameron into his office the afternoon of June 9, 1981, and likewise gave Dameron a three-day suspension pending investigation into the alleged solicitations. Dameron called Flick the next day to inquire about his employment status, whereupon Flick informed him that he had been fired.
II.
On June 21, 1981 the Union filed a charge with the NLRB alleging that the Company had violated § 8(a)(1) and (3) of the National Labor Relations Act.2 Of importance in the present appeal, the union alleged that the Company had promulgated an overly broad no-solicitation rule, had engaged in several instances of unlawful interrogation of employees, and had disparately enforced its no-solicitation rule in discharging Herbekian and Dameron, thus violating the statutorily protected right of employees to form a labor union. On August 26, 1981 the NLRB General Counsel issued a complaint.
Following a hearing the Administrative Law Judge held that Sultoni’s interrogation, for the Company, of Sangster, Bui, and Maneepanth constituted an unfair labor practice under § 8(a)(1) (J.A. 20-21). With respect to the discharges of Herbekian and Dameron, the Administrative Law Judge held that the Company’s no-solicitation rule was facially valid, but that the no-solicitation rule had been disparately enforced in violation of § 8(a)(3) (J.A. 21-23). The decision of the Administrative Law Judge that the Company had disparately enforced the rule was based on evidence that, during the year prior to the firings of [804]*804Herbekian and Dameron, there had been six unpenalized general solicitations among the employees of Les Champs and the Peacock Lounge, some of which had the approval and participation of management. The record indicates that these were social solicitations for beneficent purposes that took place at least in part on work time.
At some point in 1980 employees were solicited to buy a cake as a going-away present for Renee Sanjines, a Les Champs waiter. Sherwood Dameron was among those employees who contributed $1.00 toward the cake (Tr. 265). The cake was presented to Sanjines in the presence of the Les Champs and Peacock Lounge employees (Tr. 266).
Three general solicitations collections occurred during December 1980. Renee Loustaunau, the manager of Les Champs, helped solicit and collect money to buy the Les Champs assistant manager a blazer as a going-away gift. One employee testified that she gave $5.00 toward the blazer (Tr. 162-63). At a staff meeting in 1980 manager Loustaunau mentioned that the chefs wife was expecting a baby. Several employees, including Sherwood Dameron, contributed $1.00 apiece toward the purchase of a spoon as a gift (Tr. 232-34, 250, 266-68). In December 1980 a collection was taken in order to purchase a birthday cake for a Les Champs waiter. Sherwood Dameron was among the contributors and attended the presentation of the cake by the Les Champs waiters and a couple of people from the Peacock Lounge (Tr. 260-61).
In February 1981 four employees and manager Loustaunau contributed money toward a gift for a housekeeper who was leaving the Company’s employ (Tr. 164-65, 315-16).
In March 1981 $12.00 was collected by solicitation to buy a birthday cake for a Les Champs bartender. The cake was presented by the waiters of Les Champs and manager Loustaunau during break time (Tr. 157-58, 261-64).
The Administrative Law Judge characterized these solicitations, all of which occurred within a period of approximately one year, as “numerous and substantial” (J.A. 23). His opinion states:
[T]he record [does not] disclose any adverse Respondent reaction to any of these nonunion situations. Against this background of condoned employee and supervisory solicitations, in violation of the rule, Dameron and Herbekian began to organize for the Union. Like the nonunion solicitations, these were conducted, at least in substantial part, on worktime. However, unlike the nonunion solicitations, these were not condoned. Within a week after the union solicitation began, the non-solicitation rule was promptly and vigorously enforced with the discharge of Herbekian and Dameron. It is clear, as a matter of Board and Court precedent, that the selective and disparate enforcement of a no-solicitation rule to prevent union solicitation is unlawful.
(J.A. 23). The Administrative Law Judge therefore recommended that the Company be ordered to cease and desist from disparately enforcing its no-solicitation rule. In addition, he recommended that Herbekian and Dameron receive backpay and be offered reinstatement to their former jobs or substantially equivalent employment (J.A. 24-25).
The NLRB General Counsel and the Company filed exceptions and supporting briefs with the NLRB. In a Board decision dated August 21, 1984 the NLRB in large measure affirmed the findings and conclusion of the Administrative Law Judge, and adopted his proposed order without substantial modification (J.A. 8-9).
The Company subsequently petitioned this court for review.
III.
We must determine whether substantial evidence, see Universal Camera Corp. v. NLRB, 340 U.S. 474, 488, 71 S.Ct. 456, 465, 95 L.Ed. 456 (1951), supports the Board’s decision that the facially valid no-solicitation rule, absolutely prohibiting solicitation “of any kind,” was applied in a fashion that discriminated against the statutorily protected right of employees to form a union. The law is clear that a valid no-so[805]*805licitation rule applied in a discriminatory manner or maintained for discriminatory reasons may not be enforced against union solicitation. See Midwest Regional Joint Board v. NLRB, 564 F.2d 434, 446 (D.C.Cir.1977); William L. Bonnell Co. v. NLRB, 405 F.2d 593, 595 (5th Cir.1969).
The statutorily protected organizing rights of employees may be limited only by the legitimate interests of the employer in discipline, workplace efficiency, and property protection. In Republic Aviation Corp. v. NLRB, 324 U.S. 793, 65 S.Ct. 982, 89 L.Ed. 1372 (1945), the Supreme Court held that such cases require “an adjustment between the undisputed right of self-organization assured to employees under the Wagner Act and the equally undisputed right of employers to maintain discipline in their establishments.” Id. at 797-98, 65 S.Ct. at 985. In NLRB v. Babcock & Wilcox Co., 351 U.S. 105, 76 S.Ct. 679, 100 L.Ed. 975 (1956), a case decided after the 1947 enactment of the Taft-Hartley Act, the Court indicated approvingly that the Board, in an earlier case, had “[rjecogniz[ed] that the employer could restrict employees’ union activities when necessary to maintain plant discipline or production.” Id. at 110, 76 S.Ct. at 683. The Court again stated: “No restriction may be placed on the employees’ right to discuss self-organization among themselves, unless the employer can demonstrate that a restriction is necessary to maintain production or discipline.” Id. at 113, 76 S.Ct. at 685 (citing Republic Aviation, 324 U.S. at 803, 65 S.Ct. at 988).
In Baylor University Medical Center v. NLRB, 578 F.2d 351 (D.C.Cir.1978), this court upheld a broadly worded no-solicitation rule that prohibited “solicitation of employees ... by other employees or distribution of literature between employees during work time and/or in work areas.” Id. at 352. This court held, inter alia, that it was not an unfair labor practice for the employer to bar solicitation in the corridors of the medical center, which were defined as “work areas,” because solicitation was “the most probable potential recurrent cause of disruption in the corridors____ Having to confront the worry that employees might reduce their standards of service as part of a labor dispute seems an unnecessary and undesirable source of anxiety for persons [patients and visitors] already hard-taxed emotionally.” Id. at 356. It was therefore the disruption of the workplace rationale, extending to the corridors, that this court relied on. See also id. at 360-61 (Leventhal, J., concurring in part and dissenting in part). In this respect the court was upheld by the Supreme Court in NLRB v. Baylor University Medical Center, 439 U.S. 9, 99 S.Ct. 299, 58 L.Ed.2d 202 (1978).
Decisions of the NLRB are in accord, as stated most clearly in a 1972 decision:
The [National Labor Relations] Act establishes and protects [an employee’s] right to engage [in union solicitation], so long as there is no interference with production. Only a substantial business justification, such as a genuine interference with the progress of the work, justifies any restriction on this right of solicitation. A no-solicitation rule is presumptively, and only presumptively, valid if it is limited to prohibiting solicitation during the time an employee is expected to be working and not during breaktime, lunchtime, or the like.2 Such a rule is valid because it is presumed to be directed toward, and to have the effect of, preventing interference with production.
Daylin Inc., Discount Division, 198 N.L.R.B. 281, 281 (1972), enf'd, 496 F.2d 484 (6th Cir.1974). See also Atkins Pickle Co., 181 N.L.R.B. 935, 937 (1970); Emerson Electric Co., 187 N.L.R.B. 294, 300 (1970); Hanes Hosiery, Inc., 219 N.L.R.B. 338, 350 (1975); Sunnyland Packing Co., 227 N.L.R.B. 590, 594 (1976), enf'd, 557 F.2d 1157 (5th Cir.1977) (no-solicitation rule is permissible “provided that the rule or regulation is promulgated in good faith and bears some reasonable relation to efficient operation of the plant, and is not merely a device [806]*806to obstruct or impede self-organization.”) (emphasis added); George Washington University Hospital, 227 N.L.R.B. 1362, 1373-74 (1977) (“The factual recital shows that the prospective solicitation policy generally was widely ignored in practice in respect to non-union matters which were neither more essential to nor less disruptive of the effective functioning of the hospital than the exercise of the statutory rights here involved____”); Paceco, A Division of Fruehauf Corp., 237 N.L.R.B. 399, 401 (1978). See generally, 2 T. Kheel, Labor Law ch. 9A (1984).
Carefully developed legal doctrine indicates that restrictions on union solicitation must be justified by the employer’s legitimate concerns for workplace efficiency. This is the only sensible way to reconcile the cases in this area. Thus, a ban on solicitation on working time and in working areas is presumptively valid; conversely, an employer may not generally prohibit union solicitation or the distribution of union literature by employees during nonworking times or in nonworking areas. See NLRB v. Babcock & Wilcox, Inc., 351 U.S. at 112-13, 76 S.Ct. at 684-85; Republic Aviation Corp. v. NLRB, 324 U.S. at 797-98, 65 S.Ct. at 985. Employees may be restricted to distributing union literature and materials to nonworking time and nonworking hours. See id. Retail stores may ban solicitation from selling areas, though not from nonselling areas during break time or waiting time. Daylin, Inc., Discount Division, 198 N.L.R.B. 281 (1972), enf'd, 496 F.2d 484 (6th Cir.1974). Restaurants may ban employee solicitation during nonworking time from customer areas, see McDonald’s Corp., 205 N.L.R.B. 404 (1973), and hospitals may ban solicitation in patient care areas. See Beth Israel Hospital v. NLRB, 437 U.S. 483, 500-07, 98 S.Ct. 2463, 2473-77, 57 L.Ed.2d 370 (1978).
Disparate enforcement inherently requires a finding that the employer treated similar conduct differently. Midwest Regional Joint Board v. NLRB, supra, at 442. This is a fact-based inquiry in which the Board proceeds on a case-by-case basis. See e.g., Hammary Manufacturing Corp., 265 N.L.R.B. 57, 57 n. 4 (1982); Saint Vincent’s Hospital, 265 N.L.R.B. 38, 38-41, enf'd, 729 F.2d 730, 735 (11th Cir.1984). This court must therefore determine whether, in terms of actual interference with workplace production and discipline,3 the numerous union solicitations by Herbekian during working time and the single isolated solicitation by Dameron, while he was off duty, were substantially equivalent to the numerous condoned instances of employee non-union solicitations of money primarily for social purposes.4 This presents [807]*807two distinct questions since the solicitations by Herbekian and Dameron varied greatly.
IV.
As set forth above, notwithstanding the unconditional ban on solicitation, the Company had condoned six general instances of solicitations of its employees for social purposes during the year prior to the discharge of Herbekian and Dameron. These non-union solicitations may be characterized as the ordinary, ad hoc expressions of friendship that naturally occur among small groups of people. Most of the solicitations involved individual requests during working hours in working places for contributions of $1.00, or larger sums for the blazer, among a small group of friends and co-workers. While these solicitations probably averaged at least ten workers (making a minimum total of around 50 to 60 solicitations), they probably took only a few seconds each.
Comparing Herbekian’s union solicitations to the non-union solicitations, the former stand in marked contrast to the latter. During scarcely more than a month Herbekian spoke on twenty-two occasions with other employees about the union. These solicitations were concentrated into a short period and each contact occurred on work time in working areas in clear violation of the Company’s rule. Moreover, Herbekian violated the no-solicitation rule in a systematic fashion that was quite different from the spontaneous general social collections that had occurred on six occasions during the previous year. It is equally obvious that Herbekian’s solicitations on behalf of the union were significantly more involved than, say, a simple request to chip in for a small gift. According to Herbekian’s testimony, her solicitations on behalf of the union often involved an explanation of the comparative merits of the union’s dental, hospitalization, and legal plans (Tr. 97-98). It must therefore be concluded, after considering the comparative disruption of the workplace that resulted from the solicitations for the union by Herbekian and the solicitations of some employees for social purposes, that there is no substantial evidence that the Company disparately enforced its no-solicitation rule to the prejudice of Herbekian. The object of the rule is to protect against interference in the workplace. The interference by Herbekian was substantial, systematic, and concentrated while the interference caused by the social solicitations was comparatively minimal and irregular. Since the interference in the workplace caused by Herbekian’s solicitations substantially exceeded that condoned for social purposes, the facts do not support the Board’s finding of a disparate application of the no-solicitation rule against Herbekian.
However, when Dameron’s single union solicitation is compared with the numerous condoned non-union solicitations, a different situation is presented. Dameron is alleged to have violated the no-solicitation rule in his one short conversation with Bui and Maneepanth. According to Dameron’s testimony, the conversation lasted a total of “[l]ess than five minutes” (Tr. 299), during which time he presented some of the merits of forming a union (Tr. 286-88). Dameron spoke with five other employees regarding the union, but these conversations took place outside of work time and thus could not be considered as basis for any valid enforcement of the Company’s rule. The interference in the workplace caused by Dameron’s solicitation was substantially less than that caused by Herbekian’s solicitations and substantially less than the Company-condoned non-union solicitations. Thus, in discharging Dameron while condoning non-union solicitations that caused greater disruption of the working place, the Company disparately enforced its no-solicitation rule.
It bears repeating that the “essence of discrimination in violation of sec[808]*808tion 8(a)(3) is treating like cases differently.” Midwest Regional Joint Board v. NLRB, supra, at 442. It follows that condoning greater violations while punishing lesser violations also constitutes disparate treatment. Dameron was discharged because of his single solicitation of two employees on work time, which on its face violated the Company’s no-solicitation rule.5 Of course, the social solicitations engaged in by the Company’s employees were also admittedly in violation of the unconditional no-solicitation rule. We must decide whether, in terms of the actual disruption of the workplace, the respective solicitations were substantially equivalent.6 The [809]*809social solicitations permitted by the Company were only nominally disruptive of the workplace, but Dameron’s single solicitation of Bui and Maneepanth was even less disruptive than the social solicitations. Although the six instances of condoned general solicitations involved solicitations in which each single solicitation lasted only a few seconds, each general solicitation involved solicitation of a number of employees. Dameron’s single solicitation, while he was “off the clock,” of the two employees who were not working and might be said to have been on “waiting time”7 lasted “[l]ess than five minutes” (Tr. 299), and was thus of substantially lesser duration and intrusion than the six condoned general solicitations, which involved a total of many more employees.
For purposes of our inquiry then, the condoned solicitations and Dameron’s solicitation both violated the rule prohibiting “[s]olicitation of any kind ...” and constituted like cases that were treated differently by the Company.8 Substantial evidence therefore supports the conclusion that the Company in its discharge of Dameron disparately enforced its no-solicitation rule in violation of § 8(a)(3).9
V.
In conclusion, we affirm the Board’s holding that the Company’s discharge of Sherwood Dameron, for conduct that involved less actual interference with the workplace than the condoned social solicitations, constituted disparate treatment in violation of § 8(a)(3) of the Act. Dameron is entitled to receive backpay and reinstatement to his former job or substantially similar employment. It is noted that Dameron’s eligibility for an award of backpay is subject to mitigation by the sum of money he earned or could have earned between the time of discharge and the time of our decision.
With respect to Roxie Herbekian, her union solicitations in violation of the no-solicitation rule were substantial and concentrated and disrupted the workplace substantially more than the condoned social solicitations. Thus, her discharge did not constitute disparate treatment in violation of § 8(a)(3). The court therefore denies enforcement of the Board’s decision that the Company violated § 8(a)(3) in the discharge of Herbekian.
The Company does not challenge the Board’s decision that the Company violated [810]*810§ 8(a)(1) of the Act by interrogating employees about union activities. We therefore affirm the Board in this respect and remand the case to the NLRB for further action not inconsistent with this opinion.
Judgment accordingly.