Transplantation of allogeneic pancreatic islets for the treatment of patients with Type 1 diabetes mellitus (T1DM) is now a reality. The steady progress that has allowed for the recent successful clinical trials world-wide follows a steep learning curve and the perseverance of the international islet transplantation community. The Clinical Islet Transplant Program at the Diabetes Research Institute - University of Miami has contributed to the progress in the field with a 20-year track record. It has been a long journey and despite the intermediate success, more work is needed in order to achieve the ultimate goal of a safe and long-lasting treatment for patients with T1DM.