Despite recent advances and improved outcome, pancreas transplantation remains controversial. The purpose of this review was to study renal allograft outcome after simultaneous pancreas-kidney transplants (SPK, n = 61), kidney-alone transplants in type I diabetic patients (KA-D, n = 63), and kidney-alone transplants in nondiabetic patients (KA-ND, n = 80). Patients were matched for donor age, donor gender, donor race, interval from donor admission to procurement, DR mismatch, and recipient gender. The mean renal allograft cold ischemic time and recipient age were lower in the SPK group. Patient survival was highest in the KA-ND group (99% and 86% at 1 and 5 years, respectively), intermediate in the SPK group (90% and 78% at 1 and 5 years, respectively), and lowest in the KA-D group (89% and 66% at 1 and 5 years, respectively) (P = 0.004). similarly, renal allograft survival was higher in the KA-ND (89% and 63% at 1 and 5 years, respectively) and SPK (82% and 69% at 1 and 5 years, respectively) groups compared with the KA-D group (76% and 49% at 1 and 5 years, respectively) (P = 0.07). This difference disappeared when renal graft survival was censored for death, which probably reflects the selection bias. Actuarial pancreas graft survival was 76% and 62% at 1 and 5 years, respectively. Acute rejection (AR) was more frequent in the SPK group than in the KA-D and KA-ND groups (41% v 16% v 29%; P = 0.007). Delayed graft function (DGF), on the other hand, occurred more frequently in the KA-D group than in the KA-ND and SPK groups (66% v 55% v 38%; P = 0.08). Death as a result of a cardiovascular event occurred more frequently in the KA-D group. Cardiovascular death and renal graft failure occurred earlier in the SPK group. Cox regression analysis revealed a 1.6 and 1.8 times higher risk of renal graft failure in the SPK group when the donor was > or = 40 years old or female and a five times higher risk of graft failure in the KA-ND group in the presence of AR. Graft survival in patients with AR/DGF was lower than that in patients with no AR/no DGF in both the KA-D (71% and 63% v 100% and 100% at 1 and 5 years, respectively; P = 0.03) and KA-ND (90% and 56% v 100% and 100% at 1 and 5 years, respectively; P = 0.001) groups. Acute rejection did not affect graft survival in the SPK group. In the absence of AR, DGF had no effect on graft survival in any of the groups. Although the selection bias in favor of pancreas transplantation does not allow for definitive conclusions, our results show that outcome after SPK transplantation is acceptable and factors that influence the outcome after this procedure may be different from the ones affecting KA-D recipients.