One hundred seventeen patients with renal failure resulting from insulin-dependent diabetes mellitus received primary renal allografts from June 1970 to April 1983. Factors significantly associated with improved graft and patient survival were LRD sources (in particular, HLA-identical) and splenectomy. Variables such as transfusions, age, sex, and the administration of ALG were not significantly associated with transplant outcome. However, survival of patients and grafts has improved in recent years and continues to compare favorably with hemodialysis results. Although splenectomy might be the most important variable responsible for the improvement of our recent results, the use of ALG for rejection episodes might have contributed substantially to the improvement. Early transplantation, not analyzed in this study, might prove to be the most significant variable in the outcome of transplantation in patients with diabetic renal failure.