In a prospective study, an analysis of risk factors for the development of cytomegalovirus (CMV) infection and disease was performed on 77 renal allograft recipients. Twenty-five out of the 77 recipients (32%) had a CMV infection. Twenty-two of the recipients received triple immunosuppressive therapy (cyclosporin A, prednisolone, and azathioprine) while the remaining 55 received standard therapy (cyclosporin A and prednisolone). In 23 recipients (30%) acute rejection was diagnosed and the first positive parameter of infection occurred 22 days after rejection therapy. Infection occurred in 10 out of 18 HLA-DR7-positive recipients (56%) and in 15 out of 59 HLA-DR7-negative recipients (25%; P < 0.02). In multiple regression analysis, HLA-DR7 was found to be a significant predictor of CMV infection (P < 0.005). CMV disease was diagnosed in only 9 out of 25 recipients with an acute infection. Six recipients (67%) with CMV disease received triple therapy for maintenance immunosuppression; this was significantly correlated to CMV disease (P < 0.05) as compared to three recipients (33%) with CMV disease maintained with standard therapy. Our data suggest that HLA-DR7-positive recipients are more susceptible to CMV infection and that CMV disease is associated with triple immunosuppressive therapy.