with whom Me. Justice Douglas, Mr. Justice White, and Mr. Justice Marshall join, concurring in part and dissenting in part.
I concur in the Court’s holding that petitioners are “employers” of the maintenance workers who service the apartment buildings managed by D & F.
I dissent, however, from the holding that, for the purposes of § 3 (s)(l), “the enterprise of D & F is limited to the sale of its professional management services,” and that those services must be measured by D & F’s commissions. The record in this case leaves no doubt whatever that D & F’s enterprise activities resulted in both the sale of professional management services and rental space. While the Court acknowledges that sales of rental space are “sales made or business done” within the meaning of § 3 (s) (1), ante, at 197, it nevertheless decides that rental sales should not be attributed to D & F because, “when a lease is negotiated by D & F, its remuneration is calculated not from the proceeds derived from that lease, but only from the rentals collected during its managerial tenure, during which period it renders *203significant and substantial management services beyond its earlier service in negotiating the lease.” Ante, at 200.
To be sure, D & F’s remuneration for renting an apartment may not be subject to precise calculation at the time of the sale: compensation for the sale is derived from D & F’s percentage of monthly rent receipts, which includes D & F’s compensation for building operation and maintenance; and conceivably the building owner might terminate D & F’s management contract before the tenant makes all the monthly payments required under the lease, thus reducing D & F’s compensation for the sale of the rental space. It is also true that after selling the rental space, D & F performs other significant and substantial management services. But these rather unsurprising observations hardly supply a basis for the Court’s conclusion that: “It is clear, therefore, that the business of the D & F enterprise is not the sale of a product (the rental of realty) but a sale of professional management services,” and that such services must be measured by commissions. Neither the facts in this case, nor the plain words of §3 (s)(l), and the uncommonly unambiguous legislative history of that section support the Court’s conclusion that Congress meant to measure one particular enterprise activity to the exclusion of others.
I
Section 3 (s) (1) limits coverage under the Act to those enterprises “whose annual gross volume of sales made or business done is not less than $500,000_”1 29 U. S. C. *204§ 203 (s) (1). The term “sales” employed in § 3 (s) (1) is defined with specificity in § 3 (k) of the Act, 29 U. S. C. § 203 (k), to mean “any sale, exchange, contract to sell, consignment for sale, shipment for sale, or other disposition” (emphasis added). Those are simple and entirely unambiguous words that do not even remotely imply that only some “sales made or business done” should be measured. Clearly, §3 (s)(l), in terms, embraces the gross volume of apartment leases sold by D & F, as well as the professional management services sold by D & F to building owners.2
In addition, even were the wording of § 3 (s) (1) less clear, “[t]his is not a case where perforce we must attempt to resolve a controversy as to the true meaning of equivocal statutory language unaided by any reliable extrinsic guide to legislative intention,” Mitchell v. Kentucky Finance Co., 359 U. S. 290, 293 (1959). Senate and House Reports concerning the 1961 and 1966 “enterprise amendments” to the Act show explicitly that Congress *205intended enterprise activities to be measured by all “sales made or business done.” 3
Prior to 1961, the protections of the Act were extended only to employees who were themselves “engaged in commerce or in the production of goods for commerce,” §§ 6 (a), 7 (a), 29 U. S. C. §§ 206 (a), 207 (a). With the enterprise amendments of 1961, Congress substantially broadened the coverage of the Act to include all employees “employed in an enterprise engaged in commerce,” 75 Stat. 67, 69. But not every enterprise meeting the statutory definition in § 3 (r) of the Act was brought within the Act’s coverage. Section 3(s)(l) prescribed a. dollar-volume test that limited the Act’s coverage to those enterprises that had an “annual gross volume of sales of . . . not less than $1,000,000,” id., at 66. The Senate and House Reports show that the dollar-volume test was adopted to establish an economic standard that predicates coverage of the Act upon the size of the enterprise and its impact upon commerce. See H. R. Rep. No. 75, 87th Cong., 1st Sess., 3, 7, 13 (1961); S. Rep. No. 145, 87th Cong., 1st Sess., 6-7, 31 (1961); see also the Staff Report of Labor Subcommittee offered on the floor by Senator McNamara, 107 Cong. Rec. 5840-5842 (1961).
To insure that the term “sales” would not be given a narrow or technical interpretation that might exclude some enterprises that have the requisite dollar volume *206of business, but that do not make typical commodity sales,4 Congress amended the enterprise provisions of the Act in 1966, 80 Stat. 831, by substituting the wording “annual gross volume of sales made or business done” (emphasis added), for “annual gross volume of sales,” the term employed in the 1961 amendments. The Senate Report fully explains Congress’ reasons for changing the terminology:
“This test ... is intended to measure the size of an enterprise for purposes of enterprise coverage in terms of the annual gross volume in dollars (exclusive of specified taxes) of the business transactions which result from activities of the enterprise, regardless of whether such transactions are ‘sales’ in a technical sense.
“. . . The addition of the term ‘business done’ to the statutory language should make this intent abundantly plain for the future and remove any possible reason for misapprehension. The annual gross volume of sales made or business done by an enterprise, within the meaning of section 3 (s), will thus continue [under the 1966 Amendments] to include both the gross dollar volume of the sales (as defined in sec. 3 (k)) which it makes, as measured by the price paid by the purchaser for the property or services sold to him (exclusive of any excise taxes at the retail level which are separately stated), and the gross dollar volume of any other *207business activity in which the enterprise engages which can be similarly measured on a dollar basis. This would include, for example, such activity by an enterprise as making loans or renting or leasing property of any kind. S. Rep. No. 1487, 89th Cong., 2d Sess., 7-8 (1966). (Emphasis added.)
Congressional intent, with respect to the dollar-volume test in § 3 (s) (1), could not be more clear: “the business transactions which result from activities of the enterprise” are to be measured. No transactions are excepted from measurement. Nothing in the legislative history suggests that when remuneration for essentially different transactions is in some way commingled, or when an enterprise engages in closely related activities, only those transactions constituting the essence of enterprise should be measured. For the purposes of § 3 (s) (1), the only relevant inquiry is what activities the enterprise engages in, and what sales or business transactions result from those activities. Measurement of the dollar volume of those transactions indicates the size of the enterprise and its impact upon commerce.
Turning to the facts in this case, it is clear from the stipulated record in the District Court that D & F engages in essentially two distinct, though related, activities. First, D & F rents apartments to the public. In this connection, D & F employs a staff of sales personnel who advertise available apartments, interview prospective tenants, and negotiate and renew leases on behalf of the apartment-building owner. Second, D & F operates and maintains apartment buildings. By contract with the building owner, D & F agrees to collect rent; initiate, prosecute, and settle all legal proceedings for eviction, possession of the premises, and unpaid rent; make repairs and alterations; negotiate contracts for utilities and other necessary services; purchase supplies; *208pay all bills, including mortgage payments; prepare an operating budget for the building owner’s review and approval; submit periodic reports to the owner; and hire, discharge, and supervise all labor and employees required for the operation and maintenance of the premises. Thus, D & F performs both brokerage and management activities. Indeed, the first article of every contract entered into by D & F and a building owner states: “Owners hereby employ and appoint [¶] & F] as the sole and exclusive renting and management agent . . (emphasis added).
The business transactions resulting from these activities are quite distinct and subject to separate measurement. D & F’s brokerage activities result in the sale of rental space to the public. D & F’s management activities result in a business transaction between D & F and the building owner, i. e., D & F’s sale of professional management services.
The Court, however, focuses upon D & F’s management activities and measures only the resulting transaction between D & F and the building owners. To be sure, these transactions have an impact upon commerce and must, therefore, be measured under the dollar-volume test. As a result of these transactions, D & F hires and supervises more than 100 persons who perform all the functions necessary for the efficient operation and maintenance of apartment buildings, and thus engages in activities which clearly induce a flow of men, money, and materials across state lines. But, as significant as this impact upon commerce may be, it pales by comparison to the impact caused by D & F’s brokerage activities. To sell apartments, D & F employs a special staff of personnel whose duties include developing marketing strategies, placing advertisements in various media, interviewing prospective tenants, and negotiating *209leases. These activities generate a flow of millions of dollars per year in gross rent receipts, with consequent impacts upon commerce too numerous and obvious to trace here. The significant impact of D & F’s brokerage activities upon commerce is not diminished by the fact that the apartment buildings are owned by others. It is D & F’s brokerage activities — not the building owners’— that result in the sale of rental space. In this respect, D & F, as a broker selling rental space owned by others, is indistinguishable from the salesman of consignment goods, whose “sales made or business done,” the Court concedes, ante, at 199, must be measured by the gross receipts from sales of the product.
Ignoring D & F’s brokerage activities and their resulting transactions, therefore, not only contradicts Congress’ clearly expressed intention that transactions resulting from any activity of the enterprise be measured, but also undermines the effectiveness of the dollar-volume test as a measure of an enterprise’s size and impact upon commerce.5 “Where both the words of a statute and its legislative history clearly indicate the purpose of Congress, it should be respected,” Schwegmann *210Bros. v. Calvert Distillers Corp., 341 U. S. 384, 402 (1951) (Frankfurter, J., dissenting).
II
Even proceeding on the Court’s erroneous basic premise, however, D & F’s sales of professional management services exceed $500,000 when computed, as Congress required, under the specific regulations promulgated by the Wage and Hour Division of the Department of Labor to effectuate §3(s)(l).6 As a guide to making computations under § 3 (s)(l), Congress instructed that:
“The method of calculating the requisite dollar volume of sales or business [for enterprise coverage purposes] will be the same as is now followed under the law with respect to calculating the annual dollar volume of sales in retail and service establishments, and in laundries under the exemptions provided in section 13(a)(2), (3), (4), and (13) of the act. The procedure for making the calculation is set forth in the Department’s Interpretative Bulletin [pertaining to retailers of goods and services]. As it is there stated, the 'annual dollar volume of sales’ consists of the gross receipts from all types of sales during a 12-month period.” S. Rep. No. 145, 87th Cong., 1st Sess., 38 (1961). (Emphasis added.)
This “gross receipts” method of computation is presently embodied in regulations which state: “The annual gross dollar volume of sales made or business done of an enterprise or establishment consists of the gross receipts from all of its sales or its volume of business done during a 12-*211month period,” 29 CFR § 779.265. (Emphasis added.) See also 29 CFR §§ 779.259, 779.266-779.269.
Gross receipts from “sales” of professional services are not necessarily limited to commissions. True, if the “sale” is only of the personal labor of the seller, commissions may well be the sole measure of “sales made or business done” because commissions are the seller’s only gross receipts. And where, in addition to his own labor, the seller of professional services provides, for a commission, personnel and materials as an integral part of the professional services rendered, the commission still constitutes the gross receipts for the sale of services. If, on the other hand, the purchaser of the professional services reimburses the seller for the costs of men and material and also pays a commission, plainly “gross receipts” under the statute and regulation are the reimbursement plus the commission.
D & F was compensated for its professional management services on a cost-plus-commission basis. It employed maintenance workers and purchased materials necessary for the operation and maintenance of the apartment buildings. By contract, the building owner agreed to reimburse D & F for these operation and maintenance costs,7 and, in addition, to pay D & F a commission.8 Thus, D & F’s gross receipts must include amounts paid by the building owner to cover operation and maintenance costs, plus the amount paid as commissions.
Section 3 (r) of the Act, 29 U. S. C. §203 (r), defines “enterprise” to mean:
“the related activities performed (either through unified operation or common control) by any person or persons for a common business purpose, and includes all such activities whether performed in one or more establishments or by one or more corporate or other organizational units including departments of an establishment *204operated through leasing arrangements, but shall not include the related activities performed for such enterprise by an independent contractor . . .
The dollar-volume test of § 3 (s) (1) of the Act, 29 U. S. C. §203 (s)(l), limits coverage during the period February 1, 1967, through January 31, 1969, to those enterprises “whose annual gross volume of sales made or business done is not less than $500,000 (exclusive of excise taxes at the retail level which are separately stated) . . . .” On February 1, 1969, the dollar-volume test was reduced to $250,000. It is not disputed that each year since February 1, 1969, petitioners have met the dollar-volume requirement of the Act.
In addition to the Court of Appeals below, the Courts of Appeals for the Fifth and Tenth Circuits have held that the leasing of rental property constitutes a “sale” within the meaning of the enterprise provisions of the Act. See Wirtz v. Savannah Bank & Trust Co., 362 F. 2d 857 (CA5 1966); Wirtz v. First National Bank & Trust Co., 365 F. 2d 641 (CA10 1966).
A continuance of the judicial practice of liberal interpretation of the Act was clearly contemplated by Congress:
“In keeping with the broad statutory definitions of the coverage phrases used, the courts have repeatedly expressed and adhered to the principle that the coverage phrases should receive a liberal interpretation, consonant with the definitions, with the purpose of the Act, and with its character as remedial and humanitarian legislation.” H. R. Rep. No. 1366, 89th Cong., 2d Sess., 10 (accompanying the 1966 amendments to the Act).
Questions concerning the scope of the term “sales” in the dollar-volume provision of the 1961 enterprise amendments had arisen in suits brought by the Secretary of Labor to enforce the Act. For example, in Wirtz v. Savannah Bank & Trust Co., supra, the defendant bank contended “that the term 'sales’ must be given a 'literal interpretation’ and . . . would not include rental receipts, interest on loans and securities or income from services.” 362 F. 2d, at 862-863 (footnote omitted).
An enterprise’s dollar volume of “sales made or business done” is measured by its “gross receipts,” see part II, infra. The record indicates that D & F collected gross rent receipts of $7,752,600.86 in 1967 and $8,607,086.04 in 1968. That portion of the gross rent receipts attributable to D & F’s sales of rental space constitutes the proper dollar-volume measure of D & F’s brokerage activities. As discussed in part II, infra, D & F’s “gross receipts” for its management activities must be measured by the commissions D & F receives for such services plus any reimbursements D & F receives for the cost of men and materials. Since D & F is paid a single commission for both its brokerage and management activities, that portion representing compensation for its sale of rental space must be subtracted from the total commission in order accurately to measure that portion of the commission attributable to its professional management services.
Section 602 of Pub. L. 89-601, 80 Stat. 844, provides that the Secretary of Labor is “authorized to promulgate necessary rules, regulations, or orders with regard to the [1966 enterprise] amendments made by this Act.”
The apartment building owners never actually sent funds to D & F to cover its costs and commissions. Rather, these sums were deducted by D & F from the total receipts it collected from the tenants of each apartment building.
D & F’s commissions are either 4% or 6% of gross rent receipts, depending upon the extent of the services it agrees to render.