One hundred sixty-four patients were prospectively studied for evidence of cytomegalovirus (CMV) infection after renal transplantation to determine the effect of primary and recurrent CMV infection on early graft and patient survival. Primary infections occurred in 62% (21 of 34) of pretransplant seronegative recipients and recurrent infection infection in 93% (121 of 130) of seropositive recipients. Symptomatic infections occurred in 81% (17 of 21) of primarily infected and 31% (37 of 121) of recurrently infected recipients. CMV infections (determined by initial virus excretion) occurred in 86% of the primarily infected and 96% of the recurrently infected symptomatic recipients by the 9th post-transplant week. In contrast, only 53% of nonsymptomatic recipients excrete virus by the 9th week. Primarily infected recipients experienced a significantly lower graft survival at 6 months than uninfected seronegative or recurrently infected patients. However, there was no significant difference in patient or graft survival at 1 year. Recipients who developed recurrent symptomatic infections had a significantly lower graft and patient survival than those recipients who developed nonsymptomatic recurrent infections (P less than 0.0002 patient survival and P less than 0.001 graft survival at 12 months).