The study's population consisted of kindergarten boys in low socioeconomic areas of Montreal. To control for cultural effects, the boys were included in the study only if both their biological parents were born in Canada and the parents' mother tongue was French. A total of 319 subjects rated as significantly disruptive by their kindergarten teachers composed the sample. Ninety-six of the boys were assigned to the treatment group, and 46 families agreed to participate in the treatment program. The remainder of the sample was assigned to a no treatment contact control group and a no treatment, no contact control group. After an assessment period of 4 months, the treatment (child social skills training and parental skills training) lasted 2 school years. Behavioral ratings were obtained from teachers, peers, mothers, and subjects themselves for each year since the spring of 1987. Results from 3 years of followup (from age 9 to 12) after 2 years of treatment (from age 7 to 8) indicate that the treated disruptive boys manifested less physical aggression in school, were more often in an age appropriate regular classroom, had less serious school adjustment problems, and reported fewer delinquent behaviors compared with the untreated members of the sample. It is still too early to confirm that treatment has helped prevent juvenile delinquency. 3 figures, 2 tables, and 42 references