The complex program of insulin replacement for type 1 diabetes that is current clinical standard of care is difficult to implement for long periods of time, associated with an increased risk of severe hypoglycemia and implemented by less than 50 % of the population of such patients. Outcomes of transplantation of isolated human islets have substantially improved and been performed at about 40 institutions around the world. We are proposing a clinical phase 1/phase 2 study of islet transplantation alone evaluating safety and efficacy in five patients with type 1 diabetes. Islet isolation from deceased donor pancreases will be performed at the Mayo Rochester Islet Isolation facility and islets infused by Interventional Radiology into the portal venous system. Following islet infusion, patients will be hospitalized for 48 hours in the General Clinical Research Center (GCRC) or at the Rochester Methodist Hospital. Multiple safety and efficacy outcomes will be followed on multiple occasions during the first year and periodically thereafter.