The study was designed to determine the effect of upright-posture (UP) versus semirecumbent (SR) cycling on commonly used measures of maximal and submaximal exercise capacity. Nine healthy, untrained men (M age = 27 years, SD = 4.8 years) underwent steady-state submaximal aerobic testing followed by a ramped test to determine maximal oxygen consumption (V[subscript O2max]). Anaerobic peak and average power and total work were assessed with the Wingate test. All tests were performed in both SR and UP positions, in random order. Oxygen consumption (V[subscript O2]) and ventilation (V[subscript E]) at the maximum workrate were lower in the SR position (p less than 0.05). At submaximal workrates (50 W and 100 W), V[subscript O2] and V[subscript E] were equivalent in the UP and SR positions, despite differences in tidal volume and respiratory rate (p less than 0.05). There was no difference in peak or average anaerobic power in the two positions. In summary, SR exercise was associated with a reduced V[subscript O2max] and a significantly altered ventilatory response to aerobic exercise, with no change in anaerobic power output. (Contains 1 figure and 2 tables.)