Aim:  Calcitriol and alfacalcidol are used extensively for the treatment of secondary hyperparathyroidism. Unfortunately, there is limited published data comparing the efficacy and tolerability of both active vitamin D sterols. This study was undertaken to determine whether calcitriol provides a therapeutic advantage to alfacalcidol.Methods:  This was a randomized, active controlled study. Patients with intact parathyroid hormone (iPTH) >32 pmol/L were randomized to receive orally calcitriol or alfacalcidol after each haemodialysis for up to 24 weeks. Reduction of PTH, changes of plasma albumin-corrected calcium and phosphorus were analysed. The initial dose of alfacalcidol was twice that of calcitriol.Results:  Sixteen patients were randomized into each group. At baseline, plasma albumin-corrected calcium, phosphorus and PTH were no different between groups. At 24 weeks, PTH changes were −50.8 ± 31.8% and −49.4 ± 32.5% from the baseline in the calcitriol and alfacalcidol groups, respectively (P = 0.91). The patients who achieved target PTH of 16–32 pmol/L were 82% in the calcitriol and 67% in the alfacalcidol group (P = 0.44). Plasma albumin-corrected calcium and phosphorus were not significantly different but showed trends toward gradually increasing from baseline in both groups (calcium, 6.0 ± 7.2% vs 10.9 ± 6.5% (P = 0.10); phosphorus, 13.0 ± 29.4% vs 16.7 ± 57.2% (P = 0.83) in calcitriol and alfacalcidol, respectively). The mean dose of calcitriol and alfacalcidol were 4.1 and 6.9 µg/week, respectively (P < 0.0001).Conclusion:  Alfacalcidol can be used to control secondary hyperparathyroidism at doses of 1.5–2.0 times that of calcitriol. The two drugs are equally efficacious and lead to similar changes in calcium and phosphorus.