To investigate the effect of oral nifedipine, a calcium channel blocker known not to modify cyclosporin A (CyA) pharmacokinetics, on immediate transplant function and CyA nephrotoxicity, 68 adult renal transplant recipients were pre-operatively randomized to one of three regimes: A (high-dose CyA, initial dose 17 mg/kg per day, maintenance dose 7 mg/kg per day); B (regime A plus oral nifedipine); C low-dose CyA, initial dose 10 mg/kg per day, maintenance 4 mg/kg per day plus azathioprine 1 mg/kg per day). All three groups received identical steroid regimes. Calcium channel blockers of all types were avoided in groups A and C. Delayed graft function (dialysis dependence by day 4) was seen least frequently in group B (P < 0.02). Group B had improved graft function at 6 months compared with group A, identified by differences in serum creatinine (P < 0.05), GFR (P < 0.01) and ERPF (P < 0.05). Similar differences in serum creatinine (P < 0.05) and GFR (P < 0.05) were also identified at 12 months. Group C also had better 6- and 12-month GFR values than group A (P < 0.05 each). The three groups did not differ in donor or recipient age, HLA matching, ischaemic or anastomosis times, frequency of early rejection or whole-blood CyA levels. These results indicate that nifedipine significantly improves immediate and medium-term graft function.