A total of 793 kidney transplantations (KTx) were performed from November 1073 to March 1993. Two hundred and forty-two patients were treated with conventional immunosuppression (azathioprine + prednisolone) and all the others with cyclosporine (Sandimmun) and prednisolone (SIM + PRED). The survival of the second graft was less good in both therapeutic groups than that of the first ones, so we have started to use preventive immunotherapy with OKT3 (CILAG) in combination with SIM (both before operation) and PRED. We compared 32 SIM-PRED patients with 20 OKT3 + SIM + PRED patients. All underwent a second KTx. The two groups were found to be comparable and homogeneous with regard to 14 of 18 parameters analysed statistically. Statistically significant differences were found between the two groups as regards the frequency of acute rejection within 30 days (46.69% vs 20%), the delta creatinine value on the 1st and 2nd postoperative days (-4.3: -8 vs -8.6: -19.7%), patient survival after 4 years (78.2 vs 100%), and graft survival after 1 and 4 years (-58.9: -42.8 vs -83.5: -83.5%), with better results in the OKT3 group. We conclude that the preventive use of OKT3 simultaneously with SIM + PRED for the second KTx is the method of choice to prevent rejection and improve survival. This treatment results in patient and graft survival following the second KTx being as good as after the first KTx with SIM + PRED.