Energy consumption data were obtained on 8 normal subjects ambulating with underarm crutches, using a 3-point gait at 30, 40, 50, 60, 70, and 80 meters per minute (m.min-1) on level terrain, and 40, 60m.min-1 on a 5% grade, and climbing 19-cm stairs at 16 and 24 steps/minute. The subjects ambulated without crutches at 30, 50, 70m.min-1 on the level, 60m.min-1 on a 5% grade, and stairs at 16 and 24 steps/minute. Oxygen consumption (VO2) and ventilation data were obtained from a portable device. Respiratory quotients were determined from samples of expired gas. Maximal upper extremity(bicycle ergometer) and lower extremity (treadmill) stress tests were determined. The energy cost (oxygen consumption) VO2.wt-1 (ml.min-1.kg-1) of ambulating with underarm crutches compared to normal walking was approximately twice as great. The heart rate (HR) and VO2 for any given rate of vertical rise tested was less with crutch stair climbing than with crutch walking. There was no difference in VO2 or HR when ambulating with underarm compared to forearm (Lofstrand) crutches.