Nine male collegiate swimmers (EXP) were studied 8 d before (PRE) and 1 d after (POST) shaving the hair from their arms, legs, and exposed trunk. A control group (CON, N = 4) of their teammates was also tested at these times but did not remove body hair. In PRE and POST, distance per stroke (SL), VO2, heart rate (HR), and post-swim blood lactate concentration (BL) were measured during a 365.8 m breaststroke swim at approximately 90% effort. Subjects also performed a tethered breaststroke swim with retarding forces of 6.27, 7.75, and 9.26 kg. The EXP group experienced a significant (P less than 0.05) reduction in BL (mean +/- SE: 8.48 +/- 0.78 to 6.74 +/- 0.74 mmol.l-1), a decreased VO2 (3.60 +/- 0.15 to 3.27 +/- 0.14 l.min-1), an increase in SL (2.07 +/- 0.08 to 2.31 +/- 0.10 m.stroke-1), and an insignificant (P = 0.08) decline in HR (174 +/- 5 to 168 +/- 4 beats.min-1) during the free swim. The CON group showed no changes in BL, SL, or HR. During the tethered swim, there were no significant PRE-POST differences in VO2, HR, or BL for either group. In a separate group of swimmers (nine who shaved body hair and nine controls), removing body hair significantly reduced the rate of velocity decay during a prone glide after a maximal underwater leg push-off. It is concluded that removing body hair reduces active drag, thereby decreasing the physiological cost of swimming.