OBJECTIVE We sought to examine the relationship between reproductive history and measures of selected gonadotrophins and steroid hormones among post-menopausal women. Previous studies have suggested that there is a negative correlation between parity and post-menopausal serum estrogens, which may be a mechanism by which pregnancies protect women from the development of breast cancer. METHODS We analyzed women who experienced a natural menopause within the Healthy Women Study cohort both 1 and 8 years after menopause. Lifetime reproductive history was obtained and blood was assayed for estrone, estradiol, androstenedione, testosterone, follicle stimulating hormone (FSH), and luteinizing hormone (LH) at 1 year post-menopause and for many of these steroid hormones at 8 years post-menopause. Also at 8 years post-menopause, a hip bone mineral density measure was obtained. RESULTS Age at menopause related to a modest increase in estrone at 1 year but a decrease in estrone and estradiol at eight years. Adjustment for body mass index (BMI), oral contraceptive use, alcohol use, cigarette smoking, and education had little impact on these findings. There were no other internally consistent relationships between reproductive variables and steroid hormones or hip-bone mineral density. CONCLUSIONS These observations do not support the hypothesis that parity acts to diminish endogenous levels of post-menopausal estrogens.