To determine the safety, efficacy, and effects on glycemic control of electroconvulsive therapy (ECT) in insulin-requiring type 2 diabetic patients. Chart review was conducted of 19 patients with insulin-requiring type 2 diabetes mellitus who underwent ECT at Mayo Clinic (Rochester, Minnesota) between 1993 and 2000. None of the patients received oral hypoglycemic drugs. Daily fasting blood glucose concentrations and daily insulin requirements were determined. For each patient, the daily insulin requirements before the first ECT treatment were compared with insulin requirements after the last ECT treatment. In addition, the insulin requirements 1 day before and 1 day after each ECT treatment (n = 143) were compared. Charts were reviewed for activity, appetite, and weight changes. The average change in daily insulin requirements 1 day before the initiation of ECT compared with 1 day after the completion of ECT was not statistically significant. Changes in dietary or activity levels correlated with fluctuations in insulin requirements in selected individuals. There were no significant changes in acute glycemic control associated with ECT. Our findings refute previous reports of dangerous hyperglycemia or improved glycemic control due to ECT in insulin-requiring type 2 diabetes, and suggest that ECT is safe and efficacious in these patients.