Renal osteodystrophy is a well-recognized complication of chronic renal failure (CRF) and is associated with a marked morbidity. Bone mineral density (BMD) has been shown to be the best predictor of fracture risk in different circumstances. In this cross-sectional study, we measured BMD using dual photon absorptiometry at three skeletal sites of functional importance such as the lumbar spine (LS), the femoral shaft (FS) and the femoral neck (FN) in 106 patients with end-stage renal failure (11 predialysis patients and 95 patients on maintenance dialysis). These skeletal sites are characterized by various relative amounts of trabecular and cortical bone. The results indicate that decreased bone mass was detectable in all skeletal sites before the beginning of dialysis and that BMD was negatively related to dialysis duration in LS and FS. Nevertheless, the deleterious effects of renal osteodystrophy were more pronounced at the FS level, where cortical bone is predominant. A separate analysis of BMD in both sexes revealed that females presented a more important bone loss in both cortical and trabecular bone than males. We did not find any significant difference in BMD at the three measured sites between patients on continuous ambulatory peritoneal dialysis and on regular hemodialysis. This study emphasizes the need to pay more attention to the prevention of bone loss in patients on CRF before the start of dialysis therapy, and to the fact that the female population might display a more pronounced susceptibility to bone loss.