Infections are an important cause of mortality and morbidity in renal transplant recipients. To study the impact of anti-rejection therapy on the timing of infections, the records of 599 consecutive renal transplants, performed prior to 31 December 1996 at the Royal Melbourne Hospital, were reviewed. Patients were grouped according to acute rejection (AR) episode and treatment during the first 6 months after transplantation. Group 1 [n = 168 (35%)] patients did not experience any episode of AR. Group 2 [n = 169 (35%)] patients had one or more episodes of AR and received high doses of steroids. Group 3 [n = 141 (30%)] patients had more than one episode of AR and received anti-lymphocyte antibodies in addition to high doses of steroids. Infections were more common in Groups 2 and 3 but only cytomegalovirus (CMV) disease occurred earlier in patients treated with lympholytics. Given the high incidence and early onset of CMV disease in patients receiving lympholytics and considering that an effective prophylactic protocol remains undetermined, pre-emptive treatment with ganciclovir in this high risk group appears justified.