Women may experience greater pulmonary gas exchange impairment during exercise than men. To test this we used the multiple inert gas elimination technique to study eight women and seven men matched for age, height, and VO2max (48 mlkg-1min-1) during normoxic and hypoxic (PIO2=95 torr) cycle exercise. Resting lung function was similar between genders, except for a lower carbon monoxide diffusing capacity (DLCO) in women (p<0.05). Arterial PO2 , PCO2, and alveolar-arterial O2 difference (A-aDO2) were not significantly different between genders. Despite a lower diffusing capacity for O2 (DLO2) in women, the ratio DLO2/Q (which estimates pulmonary end-capillary diffusion equilibrium) was similar between men and women and estimates of diffusion limitation during hypoxic exercise were not different between genders. Ventilation-perfusion inequality (described by the second moment of the perfusion distribution, logSDQ) increased during both normoxic and hypoxic exercise. Surprisingly, logSDQ values were slightly lower for women under all conditions (p<0.05), but this did not significantly affect gas exchange. These data indicate that these active women, despite a lower DLCO and DLO2, do not experience greater exercise-induced abnormalities in gas exchange than men matched for age, height, aerobic capacity, and lung size. Possibly fitness level and lung size are more important in determining whether or not pulmonary gas exchange impairment occurs during exercise than gender per se.