Currently, diabetes mellitus is the most common cause of renal failure in adults. However, combined pancreatic and renal transplantation (PRT) remains controversial when compared with renal transplantation alone (RTA) in diabetic recipients. We analyzed the results and morbidity in four age-matched groups--31 patients with Type I diabetes undergoing PRT before dialysis, 30 patients with diabetes who are dependent of dialysis undergoing PRT, 31 concurrent and historic patients with Type I diabetes undergoing RTA and 31 concurrent patients without diabetes undergoing RTA. All patients received cadaver donor organs and were managed with cyclosporine and prednisone immunosuppression with selective OKT3 induction. The four groups were comparable with respect to age, weight, gender, duration and severity of diabetes, dialysis type, number of retransplants, degree of sensitization, preservation time and matching. The groups differed with regard to duration of dialysis and period of follow-up evaluation, pretransplant blood transfusions, racial distribution and OKT3 induction therapy. PRT was associated with a greater morbidity rate as evidenced by a slightly higher incidence of rejection, infections and reoperations. The number of readmissions and hospitalization period during the first 12 months was also greater after PRT versus RTA. However, none of these differences were significant. No detrimental effect was noted on renal allograft function at one year; patient and graft survival was actually higher in the PRT groups. Quality of life was improved in nearly 90 percent of PRT recipients. Although the improved results after PRT may be attributed to selection bias, only lesser differences were noted among the four study groups. The aforementioned data suggest that appropriate patient selection can overcome the morbidity associated with PRT, resulting in excellent patient and graft survival with the potential for complete rehabilitation.