Fifty of 216 renal transplants performed over a five-year interval were complicated by at least one episode of septicemia. Septicemia was more frequent prior to 1966 and after a nonrelated donor transplant. The septicemic episode was due to gram-negative organisms in more than half of the cases, and the urinary tract was the commonest site of origin of sepsis. Septicemia occurred most frequently within the first six months following transplantation. However, 16% of the septicemic episodes occurred more than two years after transplantation. The mortality rate of septicemia in this series was 63%. High-dose prednisone therapy, renal failure, and hyperglycemia frequently occurred in the period just prior to the onset of sepsis.