The summer treatment program (STP) is a comprehensive intervention for attention-deficit/hyperactivity disorder (ADHD) that combines several empirically validated, behavioral treatment components in order to address multiple areas of impairment. The current study utilized a BAB treatment withdrawal design to evaluate the effectiveness of the STP. Participants included 44 children diagnosed with ADHD and comorbid disruptive behavior disorders who were enrolled in the STP. During the 6th week of the STP, behavior was measured during a planned period where all behavioral treatment components were withdrawn. Treatment was then reinstated in its entirety. Across measures of behavior, academic functioning, and teacher, counselor, and child ratings, substantial behavioral deterioration occurred during the withdrawal period, and behavior returned to previous levels upon the reinstatement of the STP treatment components. Results support the efficacy of the STP as an intervention for ADHD across multiple domains of impairment, including classroom and peer functioning.