The aim of the present study was to evaluate the insulin and glucagon responses to various stimuli in patients following pancreatic transplantation. Four Type 1 (insulin-dependent) diabetic patients with end-stage renal failure who had received a cadaveric segmental, neoprene-injected, pancreas transplant, in association with kidney transplantation, were investigated. Free-insulin, pancreatic glucagon, and growth hormone concentrations were measured after both oral and intravenous glucose tolerance tests, and following tolbutamide, arginine and arginine plus somatostatin infusions. Tests were performed 1 month (three cases) and 30 months (one case) after surgery, when no insulin administration was required. Four non-diabetic kidney grafted patients, matched for duration of graft survival and immunosuppressive treatment (steroids, azathioprine and anti-lymphocyte-globulins), served as control subjects. Impaired glucose tolerance was present in all diabetic and control patients. This was possibly related to immunosuppressive treatment. In comparison with control subjects, insulin release was normal in response to arginine and tolbutamide but was reduced in response to oral and intravenous glucose, while glucagon and growth hormone release were similar in both groups. Somatostatin was less effective in diabetic patients than in control subjects in suppressing insulin and glucagon release.