We conducted a 7‐month randomized, single, double, single‐blind comparison of calcitriol (1,25(OH)2D3) with vitamin D3 in 22 hemodialysis patients to study the effects on the biochemical abnormalities associated with osteodystrophy. Calcitriol was given for 3 mo. All patients had initial pre study calcium values ≤9.5 mg/100 ml, and phosphate values ≤4.5 mg/100 ml. Data were analyzed using the Normalized Trend Index (NTI). Calcitriol induced a rise in calcium (8.7 to 10.25 mg/100 ml) (p < 0.001) and a fall in alkaline phosphatase (p < 0.005), while D3 had no appreciable effect. The mean dose of calcitriol during treatment was 0.579 µg/day while that for D3 was 706 IU/day. The effect on serum phosphate concentration was variable. Hypercalcemia as high as 13.2 mg/100 ml occurred in 2 of 13 patients on 1,25(OH)2D3, but in every instance promptly returned to normal with dose reduction. No other adverse effects were noted with therapy. We conclude that calcitriol reverses the biochemical abnormalities of osteodystrophy. Since its effects are rapidly reversed with discontinuation, the drug is probably safe as well as effective.