To evaluate the impact of endometriosis on bone metabolism.We compared bone mineral density and biochemical markers (plasma osteocalcin, bone alkaline phosphatase, fasting urinary hydroxyproline, urinary excretion of cross-linked N-telopeptide of type I collagen) of bone turnover in forty-nine perimenopausal women undergoing laparotomy because of benign gynecologic pathology: in twenty-four of them (group A) endometriosis was diagnosed, the remaining twenty-five represented the control group (group B). Statistical analysis was performed by means of Student "t"-test; significance was set at p < 0.05.Bone density of the lumbar spine (0.898 +/- 0.325 vs 0.940 +/- 0.350) and bone markers failed to show statistically significant differences between the two groups. No significant correlation was observed between any bone density measurement and severity of endometriosis.Endometriosis does not seem to induce even in advanced stages, a reduction of bone density.