Our previous work suggests that healthy human aging is associated with sex-specific differences in leg vascular responses during two-leg cycling. The present study determined if age*sex interactions in exercising leg hemodynamics persist during small muscle mass exercise not limited by cardiac output. Thirty-one younger (20 to 30 yr; 15 men/16 women) and thirty-one older (60 to 79 yr; 13 men/18 women) healthy adults performed graded single leg knee extensions to maximal exertion. Femoral artery blood velocity and diameter (Doppler ultrasound), heart rate (ECG) and beat-to-beat arterial blood pressure (MAP, radial artery tonometry) were measured during each 3-min work rate (4.8 and 8 watts/stage for women and men, respectively). Results (mean ± SE): Despite reduced resting leg blood flow and vascular conductance, older men exhibited preserved exercising leg hemodynamic responses. Older women, by contrast, exhibited attenuated hyperemic (Young: 52 ± 3 mL min^-1 W^-1; vs Older: 40 ± 4 mL min^-1 W^-1; p = 0.02) and vasodilatory responses (Young: 0.56 ± 0.06 mL min^-1 mmHg^-1 W^-1 vs Older: 0.37 ± 0.04 mL min^-1 mmHg^-1 W^-1 ; p < 0.01) to exercise compared to younger women. Relative (% of maximal) work rate comparisons of all groups combined also revealed attenuated vasodilator responses in older women (p<0.01 for age*sex*work rate interaction). These sex-specific age differences were not abolished by consideration of hemoglobin, quadriceps muscle, muscle recruitment and mechanical influences on muscle perfusion. Collectively, these findings suggest that local factors underlie the sex-specific effects of aging on exercising leg hemodynamics in healthy adults.