Infections complicated the course of 59 of 111 renal transplantations (53%) performed on 93 patients at the University of Maryland Hospital. Infections and resultant deaths were more common among the patients with cadaver transplants. The transplant wound and the urinary tract were the most common sites of infection, occurring in 33% and 24% respectively. Septicemia developed in 11 patients (10%), secondary to urinary tract infection in six and to surgical wound infection in three. Opportunistic viral, fungal, and actinomycotic infections occurred in ten patients (9%). A total of nine patients (8%) died as a result of infection. This experience with sepsis and mortality, substantially lower than previously reported, may have resulted from (1) rigorous screening and detailed histories of recipients and donors for infection at the time of transplantation, as well as bacteriologic and serologic studies; (2) discontinuation of azathioprine whenever the WBC fell to less than 5,000/cu mm; (3) aggressive surveillance and early management of infections; and (4) prompt removal of a nonviable kidney when detected by radionuclide scan and percutaneous renal biopsy.