BACKGROUND Infection is a frequent postoperative complication in renal transplant recipients. However, little information is available concerning the effect of pretransplantation dialysis modality on posttransplantation complications including infection. We therefore evaluated the effect of hemodialysis (HD) versus peritoneal dialysis (PD) on the incidence of postoperative infection as well as several other posttransplantation outcomes. METHODS A retrospective analysis was performed using medical records covering the period 30 days after transplantation of 156 dialysis patients who underwent renal transplantation at a single center during a 22-month period. Of these patients, 103 received only HD, 32 received only PD, 13 received PD in the past and HD immediately before transplantation (PH/HD), and 8 received HD in the past and PD immediately before transplantation (HD/PD). The presence of culture-proven infection, types of infecting organisms, length of initial hospital stay, and incidence of rejection during the first 30 days after transplantation were determined for each patient. RESULTS All groups were similar with regard to age, race, gender, underlying disease, donor type, incidence of delayed graft function, and perioperative antibiotic prophylaxis. There were more infectious complications within 30 days after transplantation in patients on PD just prior to transplantation (PD and HD/PD) than in HD patients (67.5% vs. 25.9%, P<0.00001). When types of infectious organisms were assessed, PD patients were found to have a greater incidence of infections with microorganisms that colonize human skin (P<0.0001). The median length of hospital stay was 3 days longer for PD patients and 6.5 days longer for HD/PD patients than for patients receiving HD (P=0.01 and 0.04), and PD and HD/PD patients were more likely to have an episode of rejection than HD patients (P=0.02). CONCLUSIONS Renal replacement therapy with PD immediately before transplantation negatively affects outcome as compared with HD, predisposing patients to a greater incidence of postoperative infections and rejection and a longer hospital stay. Further study in a randomized controlled trial may help determine how adjustment of the dialysis method can optimize transplantation outcome.