The dialysate magnesium concentration (dMg) was reduced from 1 to 0.5 mEq/l in a group of patients on chronic hemodialysis (RDT). Serum parameters and bone biopsy findings were evaluated before and after a 1-year period on the lower dMg. All patients were receiving only calcium carbonate before and during the study period. Serum magnesium (sMg) decreased significantly and fell in the normal range with low dMg, whereas the other serum parameters did not change significantly except serum phosphorous which increased, still remaining within the normal limits. Furthermore, a significant reduction of the osteomalacia pattern (evaluated by osteoid volume, osteoid surface and osteoid thickness index) was observed in all patients after 1 year on dMg of 0.5 mEq/l, whereas there was no significant variation in bone resorption patterns (resorption surface and osteoclasts). Therefore, normal sMg is recommended in RDT patients, by arranging their dMg according to individual need, in the hypothesis that high bone Mg content, attributed to hypermagnesemia, could interfere with the mineralization process.