Difficulty in social functioning, especially in the context of a peer group, is one of the defining features of Asperger's disorder. A number of specific deficits in social behavior and cognitions have been identified as underlying the pervasive social problems experienced by these children. Although treatment guidelines recommend the use of behavioral modification to increase social interactions and integration, few studies evaluate treatment effectiveness of specific interventions. In this report, the authors describe the responses of 4 boys with Asperger's disorder to an intensive and comprehensive intervention developed for children with attention-deficit/ hyperactivity disorder, the Summer Treatment Program. This naturalistic, 6-week-long behavioral program produced substantial positive changes in the boys' behavior, social skills, and social relationships. The potential effective components of the program are discussed. © 2008 Sage Publications.