Attention Deficit Hyperactivity Disorder (ADHD) is a common childhood condition. It is associated with social and emotional problems which often persist through adolescence and adulthood. Stimulants, the most common treatment, have not affected long-term outcome, nor have other treatment modalities, either alone, or in combination with medication. Clinical reports suggest that multiple interventions may have far reaching short and long-term effects. The proposed study aims to evaluate stimulant medication combined with a multimodal treatment consisting of training in social and academic skills, remedial tutoring, school monitoring, parent training and counselling, and individual psychotherapy. Using a randomized, parallel group design in two study centers (New York and Montreal), the short-term (3-12 months) and long-term (2 years) outcome of ADHD children receiving intensive (weekly) comprehensive interventions for one year and intermittently (monthly) for a second year will be compared to two treatments. The first will consist of stimulant medication and professional attention equal in time to the multimodal treatment, but not in the specific content. The second will be the typical clinical management of ADHD consisting of stimulant medication with management and crisis intervention. It is predicted that multimodal treatment will lead to significantly more improvement in social, academic, and overall functioning, and that the advantage will persist beyond the period of intensive intervention. It is also predicted that compared to controls, a greater percentage of multimodal treated children will be able to be maintained off medication after the first year of treatment.