The aim of this study was to investigate infectious complications in renal transplant recipients (RTRs) receiving mycophenolate mofetil (MMF) for prevention of acute transplant rejection. A group of RTRs (n = 47) receiving 1.0-2.0 g/day of MMF with cyclosporine A (CsA) and prednisolone to maintain immunosuppression was compared with a group (n = 47) taking triple immunosuppressive therapy including azathioprine. In both groups the etiology and incidence of infections were evaluated. During 2 years post-transplant, various infections developed in 72.3% of patients who received MMF and in 93.6% of those who received azathioprine. The incidence of viral infections was 53.2% in the MMF group and 59.6% in the azathioprine group and the incidence of bacterial infection was 55.3% and 70.2%, respectively There were two cases of active tuberculosis in the azathioprine group and one in the MMF group. MMF 1.0-2.0 g/day does not increase infection rates in RTRs compared with azathioprine.