Ulnar and posterior tibial motor nerve conduction velocity (NCV) was assessed in 91 athletes and nonathletes. The athletes included male weight lifters, swimmers, jumpers and male and female track sprinters and distance runners. NCV of the weight lifters was significantly faster than that of the other groups for both motor nerves. The male marathoners had the slowest posterior tibial NCV of all subject groups. A discriminant function analysis was successful in classifying 50.6% of the subjects into power-type, endurance-type, or untrained categories, based on ulnar and posterior tibial nerve conduction velocities. These results suggest that both genetic and environmental factors are important determinants of motor nerve conduction velocity.