This paper reports the results of a large-scale analysis of a nationwide disease management program in Germany for patients with diabetes mellitus. The German program differs markedly from "classic" disease management in the United States. Although it combines important hallmarks of vendor-based disease management and the Chronic Care Model, the German program is based in primary care practices and carried out by physicians, and it draws on their personal relationships with patients to promote adherence to treatment goals and self-management. After four years of follow-up, overall mortality for patients and drug and hospital costs were all significantly lower for patients who participated in the program compared to other insured patients with similar health profiles who were not in the program. These results suggest that the German disease management program is a successful strategy for improving chronic illness care.