BACKGROUND Simultaneous pancreas-kidney transplantation (SPKT) is a promising therapy for type 1 diabetes mellitus with chronic kidney disease. Although the long-term outcome of SPKT is extensively documented, the incidence of early complications within the first weeks after the surgery is less described. The aim of this study was to assess the incidence, causes, and risk factors of early relaparotomy after SPKT. METHODS All SPKT performed in the university hospital between 2005 and 2008 were enrolled. The primary endpoint was defined as the need for at least one relaparotomy after SPKT within the initial hospital stay. The secondary endpoints were the incidence of vascular graft thrombosis, postoperative sepsis, patient, and graft survival. RESULTS Sixty-one patients were included. During their initial hospital stay, 27 (44.3%) SPKT recipients required at least one relaparotomy. The main causes of relaparotomy were hemorrhage (59.3%) and vascular graft thrombosis (22.2%). First relaparotomy occurred at a median postoperative time of 1 day (interquartile range, 1-6). Pretransplant dialysis and nontraumatic cause of donor brain death were identified as independent risk factors for early relaparotomy. Thirty-two patients (52.4%) experienced a symptomatic or asymptomatic vascular graft thrombosis. CONCLUSIONS The early postoperative period remains a high-risk phase for relaparotomy. The selection of recipients before initiation of long-term dialysis and of donors deceased from traumatic causes may reduce the rate of these early complications after SPKT. Vascular graft thrombosis and bleeding are two major issues that arise during this critical period, suggesting the importance an adequate management of postoperative anticoagulation and hemostasis.