Ten physically active male paraplegics (means = 30 +/- 1 yr), with lesion levels ranging from T5 to L4/S2, underwent two incremental exercise tests to exhaustion. The exercise tests were arm cranking, utilizing an electronically-braked arm cranker, and wheelchair propulsion on a motor-driven treadmill. The subjects were randomly assigned to groups, and the exercise tests were separated by 1 wk. For the first six subjects, during both modes of exercise, VO2, VCO2, R, VE, and heart rates were recorded throughout; for the remaining four subjects the same variables were recorded after the heart rate reached 160 b X min-1. The VO2 (l X min-1 and ml X min-1 X kg-1), VCO2 (l X min-1), HR, and VE BTPS (l X min-1) were significantly higher at the termination of the wheelchair exercise than at the termination of the arm cranking exercise. The minute ventilation, when recorded throughout both exercise tests, showed a relatively linear phase at first, followed by a curvilinear phase. The findings of this study indicate that in the present group of paraplegics, the highest VO2 was obtained during maximum wheelchair exercise.