After this Court ruled that the term "workweek" in the Fair Labor Standards Act of 1938 (FLSA) included the time employees spent walking from time clocks near a factory entrance to their workstations, Anderson v. Mt. Clemens Pottery Co., 328 U. S. 680, 691-692, Congress passed the Portal-to-Portal Act of 1947, which, inter alia, excepted from FLSA coverage walking on the employers premises to and from the location of the employees "principal activity or activities," §4(a)(1), and activities that are "preliminary or postliminary" to "said principal activity or activities," §4(a)(2). The Act did not otherwise change this Courts descriptions of "work" and "workweek" or define "workday." Regulations promulgated by the Secretary of Labor shortly thereafter concluded that the Act did not affect the computation of hours within a "workday," 29 CFR §790.6(a), which includes "the period between the commencement and completion" of the "principal activity or activities," §790.6(b). Eight years after the enactment of the Portal-to-Portal Act and these interpretative regulations, the Court explained that the "term principal activity or activities ... embraces all activities which are an integral and indispensable part of the principal activities, " including the donning and doffing of specialized protective gear "before or after the regular work shift, on or off the production line." Steiner v. Mitchell, 350 U. S. 247, 256.

In No. 03-1238, respondent employees filed a class action seeking compensation for time spent donning and doffing required protective gear and walking from the locker rooms to the production floor of a meat processing facility owned by petitioner IBP, Inc. (IBP), and back. The District Court found the activities compensable, and the Ninth Circuit affirmed. In No. 04-66, petitioner employees sought compensation for time spent donning and doffing required protective gear at a poultry processing plant operated by respondent Barber Foods, Inc. (Barber), as well as the attendant walking and waiting times. Barber prevailed on the walking and waiting claims. On appeal, the First Circuit found those times preliminary and postliminary activities excluded from FLSA coverage by §§4(a)(1) and (2) of the Portal-to-Portal Act.

Held:

1. The time respondents in No. 03-1238 spend walking between changing and production areas is compensable under the FLSA. Pp. 7-15.

(a) Section 4(a)(1)s text does not exclude such time from the FLSAs scope. IBP claims that, because donning is not the "principal activity" that starts the workday, walking occurring immediately after donning and immediately before doffing is not compensable. That argument, which in effect asks for a third category of activities--those that are "integral and indispensable" to a "principal activity" and thus not excluded from coverage by §4(a)(2), but are not themselves "principal activities" as defined by §4(a)(1)--is foreclosed by Steiner, which made clear that §4 does not remove activities that are "integral and indispensable" to "principal activities" from FLSA coverage precisely because such activities are themselves "principal activities." 350 U. S., at 253. There is no plausible argument that these terms mean different things in §4(a)(2) and in §4(a)(1). Under the normal rule of statutory interpretation, identical words used in different parts of the same statute are generally presumed to have the same meaning; and in §4(a)(2)s reference to "said principal activity or activities," "said" is an explicit reference to the use of the identical term in §4(a)(1). Pp. 10-12.

(b) Also unpersuasive is IBPs argument that Congress repudiation of the Anderson holding reflects a purpose to exclude the walking time at issue. That time, wh