We studied the arterial pressure response to maximal leg exercise in 15 healthy volunteers at 29 and 35 weeks' pregnancy and at 8 weeks post partum. Resting mean arterial pressure at 35 weeks' gestation was similar to the postpartum control value of 88 mm Hg (range 73 to 111), but it was reduced by 10% at 29 weeks' gestation. Voluntary maximal effort averaged 2470 N (range 1450 to 3030) in the postpartum period, was similar at 29 weeks, and was reduced by 13% at 35 weeks' gestation. Mean arterial pressure showed a linear increase with force to a median maximum value of 131 (104 to 159) mm Hg, or 49% above the resting value in the postpartum period. The pressure response was unaffected by pregnancy, but was inversely related to maximal force, i.e., the individual's capacity to perform isometric exercise.