In this study the alactic anaerobic and aerobic power of top level sprinters, long-distance runners, and untrained students were compared. Maximal oxygen uptake was measured during the progressive test on a treadmill. The anaerobic power was estimated according to a newly developed bicycle ergometer technique. As reported elsewhere, the maximal oxygen uptake is very high in twelve long-distance runners (77.6 +/- 2.7 ml/kg . min-1) whereas the maximal oxygen uptake of six sprinters amounts to 60.1 +/- 5.9 ml/kg . min-1. The average alactic anaerobic power of a control group of 32 students was 710 W or 10.1 +/- 1.2 W/kg. Significantly lower results were obtained by long-distance runners (551 W or 8.93 W/kg) whereas significantly higher results were obtained by sprinters (1,021 W or 14.16 W/kg). In top level athletes, but not in the control group, a negative relation was found between aerobic power and anaerobic power.