Between January 1983 and June 1990, 32 simultaneous pancreas and kidney transplantations were performed at the University of Barcelona. Insulin-secretion was assessed by intravenous glucose tolerance test performed 24h after transplantation and oral glucose tolerance test during the follow-up. Insulin secretion was also studied in seven non-diabetic patients with kidney transplants. Insulin levels in patients with pancreas and kidney transplantations both at the basal level and after glucose stimulation were higher than normal but not different than those observed in patients with kidney transplantation only. Patients with both pancreas and kidney transplantations and kidney transplantation only presented a mild insulin resistance, measured by the glucose/insulin ratio. Insulin levels during the follow-up of a patient with portal venous drainage were similar to those observed in patients with systemic venous drainage. In conclusion, pancreas transplantation allows a long-term maintenance of glucose homeostasis, although coexisting with an insulin resistance, probably related of the immunosuppressive therapy.