To study the influence of gender on peak oxygen uptake and on the hemodynamic response to dynamic exercise in essential hypertension, 45 male and 45 female patients, matched for age and blood pressure, were studied. Blood pressure was measured intra-arterially and cardiac output by the direct oxygen Fick method. Anthropometric gender differences were accounted for by statistical adjustment for height and weight. The increase of absolute and adjusted stroke volume from sitting at rest to submaximal (50 W) and to peak bicycle exercise was smaller in women than in men (P < 0.05). At 50 W, oxygen uptake (0.96 vs 0.97 l.min-1) and cardiac output (10.9 vs 11.2 l.min-1) were not different between women and men, due to the steeper exercise-induced rises of heart rate (P < 0.001) and arteriovenous oxygen difference (P < 0.05) in the women. Women reached the same peak heart rate as men (168 vs 173 b.min-1), so that the lower (P < 0.001) stroke volume (77 vs 99 ml) and cardiac output (12.9 vs 17.0 l.min-1), together with the lower hemoglobin concentration, contributed to their impaired peak oxygen uptake (P < 0.001), both before (1.35 vs 2.17 l.min-1) and after adjustment for body size (1.44 vs 2.07 l.min-1). In conclusion, at fixed submaximal exercise, women achieve the same oxygen uptake and cardiac output as men despite a lower stroke volume, through adaptations of heart rate and peripheral oxygen extraction; their peak aerobic power and cardiac output are, however, substantially lower than in men.