The "Second Step"[R] violence prevention curriculum was implemented in a large urban school district as part of a comprehensive three-year initiative to impact students at-risk for violence and substance abuse. An outcome evaluation was conducted to assess the intervention's effectiveness on students' attitudes and on behaviors important for accountability. Results indicated improvements in students' prosocial attitudes and behaviors that were consistent across two large cohorts of students. Implications for theory and future research are discussed. (Contains 5 tables.)