Ketoconazole-Tacrolimus-Transplantatio Abstract In developing countries, kidney transplantation is greatly hindered by financial problems, especially due to costly newer immunosuppressive medications. Ketoconazole increases blood levels of tacrolimus and cyclosporine through inhibition of cytochrome P450 microsomal enzymes. We previously reported on the 6-month safety and the outstanding impact on treatment costs of ketoconazoletacrolimus combination in kidney transplant recipients. Data about this combination are still lacking in the literature. We hereby report on the long-term results of our trial. This prospective, randomized study included 70 live-donor kidney transplant recipients receiving tacrolimus (age 16-45 years, 54 males and 16 females). Patients were randomized into two equal groups: group I, for whom ketoconazole 100 mg/day was added, and group II (control group). After 2 years, group I (ketoconazole) patients were still showing a highly significant reduction of tacrolimus dose (by 53.8%) and cost (by 52.9%) compared with control group (P<0.001) and a significant improvement in graft function in comparison to their own initial graft function (P=0.002). Allover 2 years, no side effects for ketoconazole were noted. We conclude that long-term ketoconazole–tacrolimus combination in kidney transplant recipients is safe, has an outstanding impact on treatment costs and improves graft outcome.