Chronic renal failure is associated with decreased production of active vitamin D and also results in altered lymphocyte population. We studied the effect of alfacalcidol on lymphocyte phenotype. There were 15 patients (10 males, 5 females) with a mean age of 54.3+/-14.4 years who had been on chronic maintenance haemodialysis for a mean period of 3.2+/-1.5 years. Intravenous alfacalcidol was given three times weekly during dialysis for a duration of 6 months. Our results show a significant increase in NK cells from 0.20+/-0.12 to 0.27+/-0.28 (P=0.001), without a significant change in CD2, CD19, CD4, CD8 population, and CD4/CD8 ratio. (Am J Kidney Dis 1998 Dec;32(6):1036-40)