Many of these children are currently lost to adequate treatment because appropriate services are lacking or because the children are misplaced in child welfare and juvenile justice programs where their mental health needs are not recognized. Although there is no consensus as to how serious emotional disturbances in children and adolescents should be defined, there is growing agreement regarding the issues which need to be included in such a definition. These issues include age, disability, multiagency need, mental illness, and duration of disability. Services for severely emotionally disturbed children and adolescents encompass community, State, and Federal considerations in the provision of mental and physical health care, family support, education, and an adequate environment. The Child and Adolescent Service System Program established by the National Institute of Mental Health is described, and the needs of children with chronically mentally ill parents are examined. 25 references.