In the present work we report the bone histologies obtained from the iliac crest of 49 patients on chronic hemodialysis in Maracaibo. All of them were dialyzed thrice weekly with untreated tap water containing high aluminum (Al) levels. Their mean blood Al levels were found to be higher than 100 micrograms/L. Histomorphometry was used for the diagnosis of the underlying renal osteodystrophic type. Al-staining techniques (Aluminum) were applied for detection of bone Al deposits. Additionally, bone Al content was determined quantitatively by means of graphite furnace atomic absorption spectroscopy. A mixed type of osteodystrophy (type III according to Delling's classification) consisting in the simultaneous presence of hyperparathyroid bone lesions (osteitis fibrosa, OF) and a hyperosteoidosis (osteomalacia, OM) was found in 63.3% of the studied patients. The other patients (37.7%) exhibited a pure osteomalacia (OM). Bone Al deposits at the mineralization front were observed in 70% of cases and were frequently associated with bone pain, spontaneous fractures and skeletal deformities. We conclude that bone biopsy should be performed in all patients presenting bone pain and high blood Al levels.