Background : Islet transplantation has become an established treatment option for a selected, small number of patients with type 1 diabetes mellitus. ; Objectives : Indication, options, and long-term results of islet transplantation are presented. ; Materials and methods : A compilation of original work on short- and long-term results after islet transplantation is reviewed. ; Results : With islet transplantation, results regarding glucose control (HbA1c), reduction of hypoglycemia, and preservation of function of the transplanted kidney are comparable to pancreas transplantation. While long-term insulin independence is not achieved in most cases despite multiple transplantations, the occurrence of transplantation-associated complications is much lower compared to pancreas transplantation. ; Conclusions : For patients with poor glycemic control and recurrent severe hypoglycemia, and for patients with a planned kidney transplantation, islet or pancreas transplantation should be evaluated. The former is the preferred option for patients with a high perioperative risk.