Backgroud. Simultaneous pancreas/kidney transplant (SPK) is an effective therapy that enables people with insulin-dependent diabetes mellitus (IDDM) and renal failure to maintain a more normal lifestyle, without the burdens of dialysis and insulin therapy. However, SPK has been viewed as a higher cost and higher risk procedure than kidney transplant, and it is unclear if SPK offers better health and quality of life (QOL) outcomes than insulin therapy plus kidney transplant alone (KTA). The purpose of this study is to determine which procedure affords better health and QOL outcomes. Methods. This is a prospective observational study with assessments at pretransplant and 1 and 3 years posttransplant. Patients with IDDM and renal dysfunction who received either SPK or KTA from August 1990 to September 1993 at a university transplant center were enrolled. A convenience sample of patients with IDDM and complications not seeking transplants were enrolled during the same time interval. The main outcome measures were the SF-36 Short Form Health Survey and a Satisfaction with Diabetes Therapy Scale. Results. Most health status and QOL measures improved from baseline values within each transplant group. After adjustment for diabetes severity and other baseline variables, year 3 follow-up scores of the SPK cohort were better than those of the KTA cohort for several SF-36 scales: physical functioning (P=0.038); bodily pain (P=0.047), general health (P=0.014), and the physical component summary (P=0.003). SPK recipients also reported greater satisfaction with diabetes therapy (P=0.014) and perceived more benefits to secondary complications. The KTA patients, however, had higher adjusted scores for the role-emotional subscale (P=.037) and the mental component summary (P=.037). By year 3, the SPK cohort is at the 30th and 51st percentiles of the general adult US population in self-reported physical and mental health; the KTA cohort is at the 10th and 73rd percentiles. Conclusions. At follow-up, both SPK and KTA patients report better health and quality of life but SPK patients report greater improvements than KTA patients in physical health and in areas that are diabetes specific. Although the improved physical outcomes of SPK patients are consistent with perceived benefits to secondary complications, the mental health differences cannot be explained by the study data and warrant further study.