Objective: The objective of this study was to evaluate the effectiveness of a 2-week therapeutic summer day camp for children with ADHD, which included a social skills training program and parent psychoeducation and training program. This was an open-label, nonrandomized Phase I Clinical Intervention Trial. Method: Parents completed the Weiss Functional Impairment Rating Scale (WFIRS) and the Conners' Global Index--Parent Version (CGI-P), and children completed the Index of Peer Relations (IPR). All questionnaires were completed prior to the camp and 3 weeks after starting school. A total of 33 children who attended the camp were compared with a group of 15 children with ADHD who did not attend camp. Results: CGI-P, IPR, and WFIRS significantly improved in the group that attended the camp but not in the control group. Effect sizes were between 0.7 and 1.6. Conclusion: The therapeutic summer day camp is effective in improving ADHD symptoms, peer relationships, and overall functioning of children. (Contains 3 tables.)