Evidence on outcomes of islet transplant is limited by small patient numbers, short followup, and lack of standardized reporting. (These issues are being addressed by the NIH-funded Collaborative Islet Transplant Registry.) Of 37 patients from three centers, 28 (76 percent) maintained insulin independence at 1 year (published evidence); similarly, 50 to 90 percent of 104 patients from four centers were insulin independent (supplemental evidence). Serious adverse events, including portal vein thrombosis and hemorrhage, occur infrequently. Data are lacking on long-term durability of the procedure, effects on diabetic complications, or long-term consequences of immunosuppression. Evidence is insufficient for comparison with whole-organ pancreas transplant.