A study was conducted to investigate the determinants of exercise intensity using a rowing ergometer from the viewpoint of effects on oxygen uptake. Eight healthy males performed incremental exercises for three minutes at each intensity on a rowing ergometer and a bicycle ergometer, which were controlled to exert a constant preset power. Rowing pitches were set at 17, 20 and 25 strokes/min. Mechanical power for the rowing ergometer, heart rate, and oxygen uptake were measured during the final minute of each respective stage at the set load. The mechanical power which was actually exerted on the rowing ergometer increased with the rowing pitch, even though it was controlled at a constant level for each respective set load. Oxygen uptake increased with rowing pitch as well as the set load. Multiple regression analysis revealed that the rowing pitch had a greater effect on oxygen uptake than the set load. Gross efficiency varied widely with the set load, from 3.6% to 18.7%, which was a lower range than that for a bicycle ergometer. The relationship between individual heart rate and oxygen uptake for rowing exercise was similar to that for cycling exercise, indicating that heart rate is preferable for the precise prescription of exercise intensity on a rowing ergometer if the HR-VO₂ relationship is previously determined.