This background paper on children's mental health indicates that less than one-third of the children who have mental health problems receive treatment. Types of mental health problems are discussed, including intellectual, developmental, behavior, emotional, psychophysiological, and adjustment disorders. Enviromental risk factors of poverty and membership in a minority ethnic group, parental psychopathology, maltreatment, teenage parenting, prematurity and low birthweight, parental divorce, and major physical illness are described. Mental health services are discussed in detail, including therapies, treatment settings, treatment in non-mental health settings, prevention, and the integration of mental health and other services. The effectiveness of various therapies and treatment settings is examined. Current federal efforts supporting mental health services are discussed. Three main conclusions are drawn: (1) many children do not receive the full range of necessary and appropriate services to treat their mental health problems effectively; (2) a substantial theoretical and research base suggests that, in general, mental health interventions for children are helpful; and (3) although there seem to be shortages in all forms of children's mental health care, there is a particular shortage of community-based services, case management, and coordination across child services systems. A glossary of terms is included. (ABL)