A critical step in addressing excess medical morbidity and mortality in persons with serious mental illness is to better understand, and seek to improve, the medical care that they receive. Medical quality deficits for persons with serious mental illnesses include problems including overuse of certain medical services such as emergency room care; underuse of some evidence-based general medical services; and misuse, or medical error. The origins of poor quality care for persons with mental disorders are rooted in interrelated contributory factors from patients, providers, and the medical and mental health systems. At a system level, at least 4 types of separation between mental and medical health care may exacerbate the problems for persons with serious mental illnesses: 1) geographic (lack of co-located medical and mental health services), 2) financial (separate funding streams for medical and mental health services), 3) organizational (difficulty in sharing information and expertise across these systems), and 4) cultural (providers' focus on particular symptoms or disorders, rather than on the patients with those problems). Research studies and demonstration programs for improving medical care in this population have spanned a continuum of medical provider involvement from psychiatrist and patient training, to on-site consultation by medical staff, multidisciplinary collaborative care approaches, and facilitated linkages between community and mental health and medical providers. Ultimately, it will be important to develop, test, and implement a range of models for improving the medical care of persons with serious mental disorders tailored to patients' needs, mental health system capacities, and local community resources.