['To assess 1,25-dihydroxyvitamin D status and the effect of vitamin concentration on transplantation outcome in renal allograft recipients.', 'Ninety patients underwent renal transplantation between 2002 and 2005. All received alfacalcidol supplementation before surgery. 1,25-Dihydroxyvitamin D concentration was determined on day 3 posttransplantation and at 1-, 6-, 12-, 18-, and 24-month follow-up.', 'Severe 1,25-dihydroxyvitamin D deficiency was noted in 83% of patients immediately posttransplantation. From 1 to 12 months thereafter, concentrations increased almost 3-fold, and remained constant to 24 months. In 50% of patients, the 1,25-dihydroxyvitamin D concentration reached a concentration of more than 30 pg/mL, similar to that in healthy volunteers; in the other 50%, the concentration reached 17.2 pg/mL. A high incidence of delayed graft function was observed in patients with 1,25-dihydroxyvitamin D deficiency (44% vs 6%). There was a negative correlation between the initial 1,25-dihydroxyvitamin D and serum creatinine concentrations at day 3 and month 6 (P < .03). Similarly, the 1,25-dihydroxyvitamin D concentration at 1 month was negatively correlated with creatinine concentration at months 1 through 24 (P < .01). Poor outcome was observed primarily in patients with 1,25-dihydroxyvitamin D deficiency; 2 patients developed cancer, 5 grafts were lost, and 4 patients died of cardiovascular events.'] Does 1,25-dihydroxyvitamin D deficiency predict poorer outcome after renal transplantation?