Five patients with insulin-dependent diabetes mellitus that received extraperitoneal segmental pancreatic transplants were functionally assessed by 75Se-selenomethionine imaging. The radionuclide findings were correlated with fasting plasma glucose and complete clinical course. This study demonstrates that 75Se-selenomethionine imaging seems to be a reliable tool for the assessment of function of extraperitoneal segmental pancreatic transplants in the first weeks after transplantation. An excellent correlation between the radionuclide accumulation and the transplant function was seen. The relative limits of this technique, however, are related to cost, since a plasma glucose will give similar information as far as organ function is concerned. Furthermore, the findings encountered with this technique will only confirm previous laboratory data, but would not be used alone to alter the clinical treatment of the patient.