To assess the effect of age at the onset of menopause over the skeleton we have determined the age and cause of menopause and bone mineral density (BMD), by dual and single photon absorptiometry of the lumbar spine, the proximal femur and the radius shaft on 1050 osteoporotic women (suffering with at least one atraumatic vertebral fracture). The mean ± 1 S.D. menopausal age was 47.1 ± 7.6 years. The onset of menopause occurred prior to age 45 in 22% (premature), after age 52 in 9% (late), and between 45 and 52 years of age in 69% (normal menopausal age). When the osteoporotic women were categorized into three groups according to the age of menopause, those osteoporotic with premature menopause had a significantly greater frequency of hip fractures, a significantly lower age, weight and BMD over the spine, proximal femur and radius shaft compared with those of normal menopausal age. In turn, patients with late menopause had a significantly increased weight and BMD over the spine. These findings indicate that among patients with vertebral osteoporosis those women with premature menopause had a more severe bone loss and a significantly greater frequency of hip fractures.