Compared were two samples of 173 and 95 aggressive and normal 5- to 8-year-old boys on measures of verbal and cognitive development. Aggressive boys were significantly lower than normal boys on nonverbal tests but not on verbal tests. The pattern of test performance which distinguished aggressive and normal was consistent with the hypothesis that aggressive boys were delayed in developing use of verbal mediation activity despite adequate language skills. A program titled "Think Aloud" was developed to teach use of verbal mediation activity in both social and nonsocial problem solving activity. Initial trials with 6 weeks of individual sessions with 12 second grade aggressive boys showed improved prosocial behavior and normalization of the cognitive test pattern in the treated boys. Two subsequent trials working with dyads of aggressive boys were less successful. In the final project, the Think Aloud program was taught to 19 public school teachers and results compared with a self-esteem program titled Great Expectations. Few significant differences were obtained between the programs. It was concluded that both Think Aloud and Great Expectations had beneficial effects on behavior and cognitive test performacne in young aggressive boys. (Appended materials include instructions for the classroom observation form and the manual for the Great Expectations program.) (Author/SBH)