OBJECTIVE: To evaluate the effectiveness of a cluster visit model led by a diabetes nurse educator for delivering outpatient care management to adult patients with poorly controlled diabetes. RESEARCH DESIGN AND METHODS: This study involved a randomized controlled trial among patients of Kaiser Permanente’s Pleasanton, CA, center who were aged 16-75 years and had either poor glycemic control (HbA1c > 8.5%) or no HbA1c test performed during the previous year. Intervention subjects received multidisciplinary outpatient diabetes care management delivered by a diabetes nurse educator, a psychologist, a nutritionist, and a pharmacist in cluster visit settings of 10-18 patients/month for 6 months. Outcomes included change (from baseline) in HbA1c levels; self-reported changes in self-care practices, self-efficacy, and satisfaction; and utilization of inpatient and outpatient health care. RESULTS: After the intervention, HbA1c levels declined by 1.3% in the intervention subjects versus 0.2% in the control subjects (P < 0.0001). Several self-care practices and several measures of self-efficacy improved significantly in the intervention group. Satisfaction with the program was high. Both hospital (P = 0.04) and outpatient (P < 0.01) utilization were significantly lower for intervention subjects after the program. CONCLUSIONS: A 6-month cluster visit group model of care for adults with diabetes improved glycemic control, self-efficacy, and patient satisfaction and resulted in a reduction in health care utilization after the program.