The present study examined the relationship between endogenous estradiol and progesterone levels and cardiovascular activity at rest and during stress in healthy young women. Subjects were rested in both the follicular and luteal phases of the menstrual cycle. Results indicated that, during the luteal phase, higher levels of estradiol were associated with lower levels of cardiac output responses to the combined video game and speech tasks, and lower levels of heart rate and systolic blood pressure responses to the cold presser; estradiol levels were also associated positively with PEP responses to the cold presser but only under high levels of progesterone. Additionally, during the luteal phase, higher levels of progesterone were associated with higher TPR and lower stroke volume responses to the cold presser. Tn contrast, during the follicular phase, higher levels of progesterone were associated with lower vascular resistance responses to the cold presser. Consistent with data from studies using exogenous estrogens, these results suggest that estradiol may contribute to a lowering of cardiovascular responses to stress. Copyright 1996 Elsevier Science Ltd.