Severe resistance to subcutaneous insulin with normal sensitivity to intravenous insulin developed in a 39 year old woman affected by type 1 diabetes mellitus. The patient had been treated for ten months with continuous intravenous or intraperitoneal insulin before undergoing pancreatic transplantation. After surgery repeated plasmapheresis were performed and immunosuppressive therapy was undertaken. When studied again, one month after surgery, the patient showed normal sensitivity to subcutaneous insulin. Our data suggest that plasmapheresis and/or immunosuppressive treatment could have played a role in reversing insulin resistance.