One systematic review, one randomized controlled trial, and five non-randomized studies were identified regarding the clinical effectiveness of islet cell transplantation compared to insulin therapy in patients with unstable type 1 diabetes. Overall, compared to insulin therapy, islet cell transplantation was associated with better glycemic control, quality of life, and some secondary complications of diabetes including macrovascular and microvascular complications. However, the results of these studies should be interpreted with caution as numerous methodological limitations were identified. One relevant economic evaluation was identified which compared the cost-effectiveness of islet cell transplantation to intensive insulin therapy in a theoretical cohort of patients with unstable type 1 diabetes. Islet cell transplantation was not cost-effective. One evidence-based guideline developed by Diabetes Canada was identified that states that patients with unstable type 1 diabetes who have preserved renal function or who have had a successful kidney transplant may be considered for islet cell transplantation (low quality evidence; weak recommendation).