A canine model of whole pancreas transplantation with pancreaticocystostomy was studied for reproducibility and long-term graft function with oral cyclosporine. The feasibility of the operative technique was established in three dogs and the graft histology at 5 days was studied. Seven pancreatectomized dogs were transplanted without immunosuppression; acute rejection was evident at a median of 10 days (range: 7-12 days). Another 14 non-pancreatectomized dogs were given oral cyclosporine (25 mg/kg per day) resulting in prolonged graft survival (P less than 0.01) with a median (actuarial) survival of 91 days (range: 8-159 days); five dogs had vascular thrombosis or graft rejection and eight dogs died with functioning grafts. Early technical loss in two dogs (8.3%) was due to arterial thrombosis. It is concluded that the model of whole pancreas transplantation was reproducible in dogs, that long-term graft function can be achieved on oral cyclosporine, and that duct patency can be maintained. Graft infarction, either primary or due to rejection, continues to complicate this model of pancreas transplantation.