Physical health problems in people with serious mental illnesses result from a complicated and interrelated set of risk factors, including adverse health behaviors such as smoking, physical inactivity, and unhealthy diet; limited access to and poor quality of medical care; and social factors including poverty, isolation, and stigma. Making meaningful improvements in the health and lifespan of individuals with mental health conditions will require action by clinicians, mental health service users, health policymakers, and public health leaders.