Nineteen competitive male endurance athletes (11 runners and 8 duathletes/triathletes) were compared to determine what effects cross‐training might have on running performance. Subjects were evaluated for a difference in maximal oxygen consumption (VO2max), running economy, running mechanics, and best 10 km performance time. The runners exhibited a significantly greater weekly training run mileage, a lower number of weekly training hours, a longer running step length, and a faster 10 km performance time compared with the multisport athletes (p≤0.05). In addition, the runners exhibited a better running economy, requiring 6.20%, 6.13%, and 6.78% less utilization of VO2maxat three standard velocities of submaximal treadmill running. These results suggest that enhancement of running performance might be best obtained by running‐specific training activity rather than from cross‐training methods.