To determine the patterns of infectious complications in renal transplant recipients in our center, we evaluated 48 patients (29 men and 19 women) who were transplanted between 1994 and 2003. The average age of the patients was 29 years. Thirty (62.5%) and 18 (37.5%) transplants were from living related and cadaveric donors, respectively. Posttransplant immunosuppression consisted of azathioprine or mycophenolate mofetil (MMF), prednisone, antithymocyte globulin (ATG), and cyclosporine or tacrolimus. The acute rejection episodes were treated with pulse doses of methylprednisolone; steroid-resistant rejection was treated with ATG or muromonab (OKT3). All patients received prophylaxis with sulfadoxine-pyrimethamine; none received prophylaxis against cytomegalovirus (CMV) infection. Thirty-nine (81%) recipients developed 77 confirmed episodes of infection; 35 (46%) episodes occurred in the early postoperative period, 28 (36%) in the first month and 14 (18%) after 6 months. According to the type of infection, there were 24 urinary tract, 16 CMV, seven herpetic, nine general septic, six fungal, four pneumonia, one disseminated nocardial, and 10 miscellaneous episodes. All 26 (100%) patients who had acute rejection episodes developed infections compared with 13/22 (59%) who did not have rejection (P < .01). There was a significant correlation between CMV disease and acute rejection and/or tacrolimus or MMF use. CMV infection occurred after the additional immunosuppressive treatment for acute rejection in 10 patients or during the use of tacrolimus or MMF in six patients. We conclude that CMV infection was the most frequent opportunistic pathogen in our renal transplant population and related to the intensive antirejection therapy, followed by urinary tract infections within 3 months after surgery.