Graft survival rates for islet transplantation in diabetic recipients are rapidly gaining ground on the success rates for pancreas transplantation. Both procedures have a success rate of roughly 80% at 2 years posttransplant in terms of evidence for functional tissue, normalizing or nearly normalizing levels of hemoglobin A1C, and prevention of recurrent hypoglycemia and the accompanying defective symptom recognition. Although the success rate for independence from exogenous insulin treatment after islet transplantation is not as high as that for pancreas transplantation, the complications attendant to islet transplantation are substantially lesser. Questions about the future of islet transplantation center around issues concerning how many islets should be required to achieve success; techniques that will improve islet viability after isolation; whether multiple islet infusions should be needed and, if so, how much time should elapse between infusions; and whether the liver is the optimal site for islet transplantation. Resolution of these problems, among others, seems destined to secure firmly a place for islet transplantation in the treatment of type 1 diabetes mellitus for the foreseeable future.