MST is a family- and home-based treatment that strives to change how youth function in their natural settings-home, school and neighborhood-in ways that promote positive social behavior while decreasing antisocial behavior. MST targets chronic, violent or substance-abusing juvenile offenders at risk of out-of-home placement. MST typically uses the family preservation model of service delivery, where therapists have small caseloads; are available 24 hours a day, 7 days a week; and provide services in the family's home at times convenient to them. The average length of treatment is about 60 hours of contact provided during a 4-month period. This approach has been effective with youth and families of various ages, socioeconomic status, and cultural backgrounds. Studies are underway to determine the effectiveness of the MST model with other populations of youth who have various clinical problems; for youth experiencing psychiatric emergencies MST may be used as an alternative to emergency hospitalization. Bibliography, references