There is evidence that skin collagen content and bone mass are influenced by estrogen deficiency, both of them declining in the years following menopause. The aim of our study was to analyze the relationship between changes in skin collagen content and bone mass during aging. A total of 76 nulliparous women who had been admitted for surgery of non-malignant processes were studied. All subjects were arranged into five age-groups (from 20 to 60 years). Bone mineral density was measured by dual photon absorptiometry and expressed in g/cm2 as the mean of the second to fourth lumbar vertebrae. Additionally, in all patients skin biopsies were taken from a non-sun exposed site in the lower abdomen (4 cm above the pubic symphysis) and osteocalcin levels were determined. Collagen decreased significantly with age after the 40s (P < 0.001) and after menopause (P < 0.001). Changes in bone mass were closely related to those detected in collagen (r = 0.586; P < 0.0001). In conclusion, our data suggest that bone mass and skin collagen decline in parallel with aging and that the hypoestrogenism developing in postmenopausal years has a significant effect on skin collagen content. Nevertheless, the question of whether osteoporosis is an intrinsic collagen disorder remains to be demonstrated.