Group treatment based on cognitive-behavioral and social problem solving strategies has been found to produce significant improvement in aggressive children. To investigate the association between clients' initial behavioral and subjective characteristics and the degree of improvement displayed on behavioral measures over the treatment period, 76 fourth, fifth, and sixth grade boys, identified by their teachers as aggressive, were assigned to one of four treatment groups: cognitive behavioral (CB), goal setting (GS), CB plus GS (CBGS), and a no treatment condition (NT). The CB treatment consisted of 12 weekly group sessions which focused on the development of interpersonal, cognitive, and problem solving skills and on inhibiting self-statements. In the GS condition, boys identified weekly classroom behavioral goals which were monitored by teachers and reinforced in group meetings. To measure behavioral change, both teacher and parental ratings of aggression and measures of self-esteem, socioeconomic status and problem solving skills were collected. An analysis of the results showed that in both cognitive behavioral conditions, greater reduction in rates of disruptive-aggressive off-task classroom behavior was predicted by having higher rates of these behaviors initially. Greater reduction in parents' ratings of aggression was predicted by having poor social problem-solving skills initially. Additional predictors of reductions in parents' ratings of aggression in one, but not both, cognitive behavioral conditions included having higher rates of somatic symptoms and poorer social acceptance by peers. Improvement within the goal setting condition was most evident in those boys who had initially poorer self-esteem. Boys in the NT condition who demonstrated the greatest spontaneous improvement on these change measures were the ones who initally were the best problem-solvers and who had higher levels of self-esteem. The cognitive behavioral conditions appeared to have most impact with those boys who were the most in need of intervention. (Author/BL)