Process measures showed a high level of compliance with recommended implementation procedures. Pre/post outcome testing on a 20-percent random sample of students showed significant reductions in reactive aggression scores and evidence of decreases in proactive aggression. Subgroup differences in program effects were noted by grade and gender. Young children may be more positively impacted by the Second Step intervention, which provides a strong argument for universal implementation as early as kindergarten and first grade. Boys apparently experienced greater benefit from the intervention compared with girls. In understanding these grade and gender subgroup differences, it is important to note that almost all of the variance in pretest-posttest change scores was predicted by high baseline levels of aggression. These findings indicate that school personnel can effectively implement evidence-based programs; however, it is important to choose the right process and outcome measures and have a reliable and practical research design. The Second Step curriculum teaches children to change attitudes and behavior that contribute to aggression and violence. It also teaches skills that can reduce impulsive and aggressive behavior in children and increase their level of social competence. The curriculum contains three components: empathy training/perspective taking, impulse control, and anger management/interpersonal problem solving. The evaluation used both process and outcome measures. The pretest was completed in October and November 2004, and data were collected on 257 students. The posttest was completed in May and June 2005 on 246 students. Both pretest and posttest ratings were available for 239 students. Measurement and instrumentation are described, along with the data analysis plan. 4 tables and 26 references