A pancreas transplantation is the only therapy capable of returning a constant, physiological euglycemic state to diabetic patients. Considering the clinical controversies in the study of infection in diabetes and the recognized effect of insulin on the oxidative metabolism of glucose in phagocytes, the present study sought to evaluate the formation of intraphagocytic oxygen-free radicals in diabetic patients undergoing simultaneous pancreas kidney transplantation (SPK). Methods Twenty-five diabetic patients undergoing SPK were compared with 25 normal individuals. Evaluation of the oxidative metabolism of leukocytes was performed using the NBT test. Results The abnormality in the pretransplant counts (19.32%–28.2%) reached normal levels at 48 hours after transplantation (45.11%–76.25%) and was maintained to the 5th day (46.28%–76.20%). Conclusion An SPK in a diabetic patient normalized the formation of intraphagocytic oxygen-free radicals.