Research has shown that social networks can act as social support systems to promote mental health and buffer psychological stress. In this selective review the authors illuminate patterns and characteristics of social networks that maintain health and help prevent illness, explore the relationship between social networks and the course and outcome of treatment for mental illness, and describe clinical network interventions that have been used to facilitate inpatient care and maximize performance of ex-patients in the community. The authors also discuss the implications of research findings for mental health practice.