The purpose of this study was to improve adjustTnent behaviors through structured group play therapy of a school-aged child who was referred for therapy because of poor relationship with his/her peers and problems in adjustment to school due to borderline intelligence. The intention of structured group play therapy was to provide restructured settings for children with difficulty in adjustment to a normal environment, so that the children were able to get experience of appropriate interactions with his/her peers. The subject was an 8-years-old boy who scored 71 of intelligence quotient and 96 of social quotient. The rest of the group consisted of one 7 years and 9 month boy and one 6 years and 6 month old boy. Although at least one of the IQ or SQ was assessed above average both tended to be withdrawn, selectively mute, and easily distracted. Each session was 60 minutes long, held semiweekly, and a total of twenty sessions were held. Pre- and post-test were designed. The assessment instruments utilized for pre- and post-test were Korean-Child Behavior Checklist and Social Maturity Scale. Quantitative assessment of the problem behaviors and social functions was conducted by the parents of the children. A month after the termination of the treatment, posttesting was conducted. The major results were as follows: I . Externalizing problems and hyperactivity in play session were reduced. 2. Externalizing problems and h::Iperactivity were reduced, and depression/anxiety, social problems, attention problems, aggressive behaviors in home were gradually reduced. 3. In post-test social problems anrl aggression were still being reduced but attention problems and emotional ability were equal to the result at the tennination of treabnent. The change of internalizing problems was not generalized, but attention problems and externalizing problems were generalized to the environment outside therapy sessions.