Diabetes mellitus is a disease that affects millions of people and their families worldwide, and is increasingly recognized to be a growing public health problem among industrialized nations. Diabetes has been associated with a variety of co-occurring conditions, including cardiovascular disease, elevated lipid serum levels, and more recently, a variety of psychiatric disorders. In addition to this, the disease has also been linked with the pharmacologic treatment of psychiatric disorders. As a result, mental health professionals working in a variety of settings will increasingly encounter patients who have co-occurring psychiatric disorders and diabetes mellitus.