The Short-Term Assessment of Risk and Treatability: Adolescent Version (START:AV; Nicholls, Viljoen, Cruise, Desmarais, & Webster, 2010; Viljoen, Cruise, Nicholls, Desmarais, & Webster, in preparation) is a clinical guide designed to assist in the assessment and management of adolescents' risk for adverse events (e.g., violence, general offending, suicide, victimization). In this initial validation study, START:AV assessments were conducted on 90 adolescent offenders (62 male, 28 female), who were prospectively followed for a 3-month period. START:AV assessments had good to excellent inter-rater reliability and strong concurrent validity with Structured Assessment of Violence Risk in Youth assessments (SAVRY; Borum, Bartel, & Forth, 2006). START:AV risk estimates and Vulnerability total scores predicted multiple adverse outcomes, including violence towards others, offending, victimization, suicidal ideation, and substance abuse. In addition, Strength total scores inversely predicted violence, offending, and street drug use. During the 3-month follow-up, risk estimates changed in at least one domain for 92% of youth, and 27% of youth showed reliable changes in Strength and/or Vulnerability total scores (reliable change index, 90% confidence interval; Jacobsen & Truax, 1991). While these findings are promising, a strong need exists for further research on the START:AV, the measurement of change, and on the role of strengths in risk assessment and treatment-planning.