In this study, kidney transplants complicated by primary CMV infection had a higher proportion of rejected kidneys and deaths than did the small number with no CMV infection or the much larger group with pretransplant antibody to CMV. The differences between seropositive patients and those with primary infection at 3 and 6 months after transplantation were statistically significant (p < 0.05). The high frequency of allograft rejection and death observed in patients who developed primary CMV infection may have been contributed to by the inherent association in our patient population between primary infection and transplants involving cadaver and parent donors. However, comparison of only those transplants involving cadaver or parent kidneys on the basis of type of CMV infection still showed a lower success rate when primary CMV infection occurred. Matching renal transplant recipients who have no antibody to CMV with donors who are also seronegative might be proposed as a logical maneuver to prevent the acquisition of CMV with the graft, thus preventing primary infection in patients who are seronegative preoperatively. This means of donor selection could be expected to reduce the incidence of symptomatic CMV infection which accompanies almost all primary infections. The data presented here also suggest that prevention of primary CMV infection will improve the success of renal transplantation in patients who would have acquired this infection with transplantation.