Mental health and primary care delivery systems have evolved to operate differently. For example, attention to multiple medical issues, health maintenance, and structured diagnostic procedures are standard elements of primary care rarely incorporated into mental health care. A multidisciplinary treatment approach, group care, and case management are common features of mental health treatment settings only rarely used in primary care practices. Advances in treatments for mental health disorders and increased knowledge of the integral link between mental health and physical health encourage mental health disorder treatment in primary care settings, which reach the most patients. Effective integration of mental health care into primary care requires systematic and pragmatic change that builds on the strengths of both mental health and primary care.