To examine hormonal status in obese, gynecologically normal women we studied 25 regularly menstruating, massively obese (mean weight, 120 kg) women participating in a weight reduction program and 25 age-matched normal weight (mean weight, 60 kg) women. Serum 17 beta-estradiol (E2), estrone (E1), androstenedione (A), dehydroepiandrosterone sulfate, testosterone, LH, FSH, PRL, and cortisol concentrations were measured during the follicular phase of the menstrual cycle. Waist to hip ratio and abdominal fat cell size were measured at the beginning of the study. The serum levels of E2 (P less than 0.04) as well as those of A, SHBG, and LH (P less than 0.002) were lower in the obese group. Consequently, the testosterone to SHBG ratio and the E1 to A ratio were higher and the LH to FSH ratio was lower in this group. Waist to hip ratio did not correlate with the levels of circulating hormones or SHBG, but an inverse correlation was found between abdominal fat cell size and A as well as the LH to FSH ratio in the nonhirsute women of the obese group. Subsequent to moderate weight reduction (13.2 kg), serum A and E1 levels (P less than 0.01) increased, and serum cortisol levels decreased (P less than 0.001). Thus, massive obesity is associated with abnormalities in hormonal balance in gynecologically symptomless women, there being an association between E1, E2, A, LH, cortisol, and relative weight and/or abdominal fat cell size.