In a case-control study performed in two centers, the incidence of delayed graft function (DGF), defined as the necessity to perform dialysis after transplantation, was analyzed according to prior treatment with continuous ambulatory peritoneal dialysis (CAPD; n = 117) or hemodialysis (HD; n = 117). The patients were matched for age, sex, HLA compatibility, and cold ischemia time. The patients were followed up for 6 months to monitor renal graft function (serum creatinine [Screa] level immediately after transplantation, at 6 weeks, at 6 months) and postoperative complications. No significant differences were found in the warm ischemia time of the graft or previous time on dialysis. DGF occurred in 27 CAPD patients (23.1%) and 59 HD patients (50.4%; P < 0.0001). The decline in Screa level after transplantation was faster in CAPD patients: the time for Screa level to decrease 50% after transplantation (T1/2Screa) was reached after 5.0 +/- 6.6 days in the CAPD group compared with 9.8 +/- 11.5 days in the HD group (P < 0.0001). A greater number of patients developed acute rejection episodes in the CAPD group (P < 0. 05), but Screa level was not different in the two groups 6 weeks and 6 months after transplantation. No differences were observed in infectious or surgical complications. This study shows that immediate renal function after transplantation is better in CAPD patients and that peritoneal dialysis should be considered as a first choice for pretransplantation therapeutic modality.