Among 40 type I diabetic patients who received a segmental pancreatic allograft with enteric exocrine diversion and had normal endocrine graft function for more than one year, 12 patients have had occasional episodes of "graft pain" associated with short-term hyperamylasemia. The symptoms usually resolved after 1-4 days. To determine possible precipitating factors, 80 such episodes were analyzed by interviewing all the patients and reviewing their files. To study the impact on endocrine graft function, the results of the serial intravenous glucose tolerance tests were plotted versus time. Episodes of late graft pancreatitis occurred at any given time between 6 and 51 months after transplantation. The frequency of bouts ranged between 1 and 31 per patient. The symptoms and clinical course were clearly different from late rejection episodes. Except for one severe case which resulted in graft loss, endocrine graft function did not deteriorate. Four conditions were found to correlate with the attacks: mental stress, alcohol and food intake, infections, and direct mechanical pressure to the pancreatic graft. We conclude that late graft pancreatitis can be distinguished from late rejection episodes and that the pancreatic graft may be more prone to acute pancreatitis than the native pancreas. The endocrine capacity of the pancreatic graft is usually not affected even by repeated attacks.