We prospectively studied 52 consecutive renal allograft recipients who retained their grafts at least three months. The transplant recipients were observed for five years or longer. Disease due to cytomegalovirus (CMV) occurred in nine (17.3%). Manifestations of disease due to CMV that were significantly more common than in chronologically matched controls in comparable periods after transplantation included fever, leukopenia, hepatic function abnormalities, pneumonia, and renal dysfunction. Life-table analyses suggested a trend of decreased allograft survival with disease due to CMV, but the difference between controls was not statistically significant. A significant inverse correlation were noted between the level of hemagglutination inhibition antibody to rubella virus reached after transplantation and allograft survival. This correlation remained statistically significant even when patients with disease due to CMV were excluded from the analysis.