The process evaluation found that although the application of the MST program was unique in the timing of service delivery and the severity of the target population, services provided adhered to the MST treatment principles and analytical model. The problems faced by the youth and families served by the MST program were multiple and severe. Recidivism rates were higher for youth when their families had mental health, criminal affiliation, and family conflict issues. The impact evaluation found that MST was not effective in decreasing recidivism rates among OCFS youth. Contrary to expectations, participation in MST was not associated with lower rates of rearrest, reconviction, or reincarceration. In both the pilot period and the post-pilot period, boys and girls who received MST services were rearrested at about the same rate as boys and girls who received usual aftercare services. Overall, rearrest rates were high, with about 85-90 percent of boys in both the MST and control groups rearrested within 3 years of release. Frequency of rearrest was also similar across the MST and control groups. The rate and frequency of rearrest were lower among girls, but still comparable across the MST and control groups. Consistent with past research, there were few subgroup differences in treatment effects. MST is a short-term, intensive treatment approach that integrates a social-ecological approach to human development with empirical research on the causes of antisocial behavior. The process and impact evaluation methodologies are described. 39 references and extensive tables and figures