SHARP, R. L. and D. L. COSTILL. Influence of body hair removal on physiological responses during breaststroke swimming. Med. Sci. Sports Exerc., Vol. 21, No. 5, pp. 576–580, 1989. 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), V̇O2, heart rate (HR), and post-swim blood lactate concentration (BL) were measured during a 365.8 m breaststroke swim at ∼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 < 0.05) reduction in BL (mean ± SE: 8.48 ± 0.78 to 6.74 ± 0.74 mmol·l-1), a decreased V̇O2 (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 V̇O2, 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.