We investigated the relationship between bone mineral density loss and mean serum phosphate level for one year in 58 men on maintenance hemodialysis who were treated with 1 alpha-hydroxycholecalciferol and calcium bicarbonate. Bone mineral density of the femur head and neck was measured twice, 8 months apart, by dual energy X-ray absorptiometry (Hologic QDR 1000). Patients were divided into two groups according to their mean serum phosphate level during the year of the study. Group A had almost normal serum phosphate levels (mean, less than 6.0 mg/dl) and group B had hyperphosphatemia (mean, greater than or equal to 6.0 mg/dl). In group A, the mean bone mineral density was 0.825 +/- 0.122 g/cm2 at the beginning of the study and 0.828 +/- 0.118 g/cm2 8 months later. In group B, these values were 0.787 +/- 0.167 g/cm2 at the beginning and 0.762 +/- 0.171 g/cm2 8 months later. Bone mineral density did not decrease in group A, but it decreased significantly in group B (p less than 0.01). For all patients, the percent increase in the bone mineral density was inversely correlated with the mean serum phosphate value for the year of the study (r = -0.274, p less than 0.05). These results indicate the importance of serum phosphate control in patients on maintenance hemodialysis, even when they are being treated with 1 alpha-hydroxycholecalciferol and calcium carbonate.