Because of the recent licensing of pneumococcal vaccine, the risk of pneumococcal infections on a renal transplant service was determined. The overall risk of infection was 7% (14 of 197 patients) over a six-year period, or 1% per year. In patients with functioning allografts, this represented a risk of 28 infections per 1,000 patient-years of follow-up. Clinically, the major presentations of pneumococcal infection were pneumonia in the patient who was rejecting his kidney and pneumococcemia of sudden onset that was often fatal. Five of the pneumococci isolated from bacteremic patients were typed; three of the isolates were types that are in the vaccine. The frequency and seriousness of pneumococcal infections in renal transplant patients suggest that pneumococcal vaccine should be given to these patients, probably before transplantation.