The effectiveness of 1alpha-hydroxycholecalciferol [1alpha-OH)D3] in healing uremic bone disease was investigated in 10 uremic patients on maintenance dialysis. Seven patients received 1alpha-(OH)D3, 2 microgram/day, for six months, and three patients served as a control group. Bone density was determined from X-rays of the second phalanx of the second digit. The apparent intestinal calcium absorption improved on treatment with 1alpha-(OH)D3, serum calcium levels and bone density significantly increased, and a significant decrease in serum alkaline phosphatase activity was observed. In one patient, reversal of uremic myopathy occurred after 17 days of 1alpha-(OH)D3 therapy.