Objective: To test the hypotheses that in children with attention-deficit/hyperactivity disorder (ADHD) (1) symptoms of ADHD, oppositional defiant disorder, and overall functioning are significantly improved by methylphenidate combined with intensive multimodal psychosocial treatment compared with methylphenidate alone and with methylphenidate plus attention control and (2) more children receiving combined treatment can be taken off methylphenidate. Method: One hundred three children with ADHD (ages 7-9), free of conduct and learning disorders, who responded to short-term methylphenidate were randomized for 2 years to (1) methylphenidate alone; (2) methylphenidate plus psychosocial treatment that included parent training and counseling, social skills training, psychotherapy, and academic assistance, or (3) methylphenidate plus attention psychosocial control treatment. Assessments included parent, teacher, and psychiatrist ratings, and observations in academic and gym classes. Results: Combination treatment did not lead to superior functioning and did not facilitate methylphenidate discontinuation. Significant improvement occurred across all treatments and continued over 2 years. Conclusions: In stimulant-responsive children with ADHD, there is no support for adding ambitious long-term psychosocial intervention to improve ADHD and oppositional defiant disorder symptoms. Significant benefits from methylphenidate were stable over 2 years.