Simultaneous pancreas and kidney transplantation (SPK) is capable of achieving normoglycemia, as assessed by oral glucose tolerance tests (OGTT), in the majority of diabetic recipients with end-stage renal disease. Despite its success over the last decade, standard ranges for OGTT after SPK are not available for comparison between studies and techniques. We examined 327 prospectively performed OGTT, undertaken in insulin-free bladder-drained SPK recipients, between 1 month and 10 yr after transplantation. Ranges of values for glucose, insulin and C-peptide were derived and areas under the time concentration curves calculated. The normal range of 2-h glucose values from SPK recipients was comparable to WHO criteria for the diagnosis of diabetes mellitus in a normal population; however, the fasting glucose fell below these levels. Fasting and area-under-the-curve (AUC) glucose were remarkably stable with time after SPK, although insulin fell with time after pancreas transplantation. These ranges may allow clinical evaluation of the endocrine function in individual SPK recipients, provide standards for comparison between different centers and techniques, and provide targets for islet transplantation.