PURPOSE: The influence of drafting was studied on the swimming performance, metabolic response, and passive drag of eight triathletes. METHODS: The performance in drafting position was measured directly behind another swimmer during a 400-m swim and compared with the nondrafting position. Metabolic response concerned VO(2), blood lactate, stroke rate, stroke length, and rating of perceived exertion. Drag was measured by passive towing. RESULTS: In drafting position, the triathletes swam on average faster (3.2%) over the 400-m swim than in nondrafting position (4 min, 47.69 +/- 10.35 s vs 4 min, 57.25 +/- 7.24 s; P < 0.01). Blood lactate and stroke rate were significantly lower (9.6 mM vs 10.8 mM; 39.9 cyclexmin(-1) vs 41.3 cyclexmin(-1) P < 0.02) and stroke length higher (2.10 mx cycle(-1) vs 1.97 mxcycle(-1), P < 0.01) than in nondrafting position. VO(2) and rating of perceived exertion were not statistically different. Passive drag was lower in drafting than in nondrafting position (P < 0.01). However, the gain in drag decreased with the towed velocity (from 26% at 1.1 mxs(-1) to 13% at 1.7mxs(-1)). In drafting position, the performance gain was related to the 400-m time (r = 0.80, P < 0.01) and to the skinfold thickness (r = 0.94, P < 0.01), with faster and leaner swimmers having greater gains of performance. CONCLUSIONS: Swimming behind another swimmer in a race is advantageous for triathletes.