The purpose of this investigation was to compare physiological responses to in-line skating and running at preferred levels of exertion. Ten males and ten females performed 15 min of in-line skating or running on two separate days. Subjects were instructed to exercise at an intensity that represented an effective cardiovascular workout. Heart rate (HR) and oxygen consumption(˙VO2) were monitored continuously using a portable, telemetric, open-circuit spirometry system. Subjects maintained steady rate˙VO2 over minutes 11-15 of in-line skating and running at speeds([horizontal bar over]X ± SD) of 21.7 ± 2.4 and 12.2 ± 2.3 km·h-1, respectively. A significantly higher (P = 0.03) ˙VO2 ([horizontal bar over]X ± SEM, 44.0 ± 1.7 ml·kg-1·min-1) was observed during running compared with in-line skating (42.0 ± 2.0 ml·kg-1·min-1), but there were no differences in ventilation, HR, or rating of perceived exertion. Consistent with the results of previous investigations, we conclude that in-line skating is an appropriate form of exercise for improving cardiorespiratory fitness. Future studies should compare the cardiovascular training effects of in-line skating and running in individuals of varying levels of fitness and skating ability.