The hormonal variations in postmenopausal osteoporosis are not precisely defined. The duration of the menopause and other factors, such as the weight of the patients, may be of significance. Having a basic criterion of uniformity in weight, sixty postmenopausal women were studied in regard to the following aspects: urinary hydroxyproline, estrone, estradiol, parathyroid hormone, thyroxine, triiodothyronine, thyroid stimulating hormone, cortisol and metacarpal cortical area/total area. They were divided into: Group A: 15 patients with osteoporosis and five years since menopause; Group B: 15 patients without osteoporosis (age-matched with group A); Group C: 15 patients with osteoporosis and more than ten years since menopause; and Group D: 15 patients without osteoporosis (age-matched with Group C). In the group with postmenopausal osteoporosis (A and C) there is a significant increase in urinary hydroxyproline/creatinine and a significant decrease of the cortical area/total area when we compared them with age-matched groups. The hormonal values do not vary significantly among the four groups. Ours results indicate an increase of bone resorption as a cause of postmenopausal osteoporosis. The hormonal variations, if any, cannot be related to basal values.