OBJECTIVE Very little research has focused on the efficacy of Adderall (Shire-Richwood Inc, Florence, KY) in the treatment of children with attention-deficit/hyperactivity disorder (ADHD), and no studies have compared it with standardized doses of Ritalin (Novartis Pharmaceuticals, East Hanover, NJ). It is thought that Adderall has a longer half-life than Ritalin and might minimize the loss of efficacy that occurs 4 or 5 hours after Ritalin ingestion. We compared two doses of Ritalin and Adderall in the treatment of ADHD in children in an acute study and assessed the medications' time courses. METHODS Within-subject, double-blind, placebo-controlled, crossover design lasting 6 weeks. As in our previous work, medication changes occurred on a daily basis in random order over days. METHODS Eight-week, weekday (9 hours daily) summer treatment program at the State University of New York at Buffalo, using an intensive behavioral treatment program including a point system and parent training. METHODS Twenty-five children (21 boys and 4 girls) diagnosed as ADHD using standardized structured interview and rating scales, mean age 9.6 years, 88% Caucasian, of average intelligence, with no medical conditions that would preclude a trial of stimulant medication. Thirteen were comorbid for oppositional-defiant disorder and another 8 for conduct disorder. METHODS Children received 10 mg of Ritalin, 17.5 mg of Ritalin, 7.5 mg of Adderall, 12.5 mg of Adderall, or placebo, twice a day (7:45 AM and 12:15 PM), in random order with conditions changing daily for 24 days. METHODS Daily rates of behaviors in recreational and classroom settings, and standardized ratings from counselors, teachers, and parents, were averaged across days within condition within child and compared. Within-subject relative sizes of the medication effects were computed by taking the placebo-minus-drug mean difference divided by the placebo standard deviation for each child, and were compared hourly between first daily ingestion (7:45 AM) and 5:00 PM to assess the time course of the two drugs. Measures were taken at 12:00 PM (recess rule violations) and at 5:00 PM (parent behavior ratings) to determine whether Adderall was still effective at times when the effects of Ritalin should have worn off. Parent ratings were also made for evening behavior to assess possible rebound, and side effects ratings were obtained from parents, counselors, and teachers. Parents, counselors, and teachers also rated their perceptions of medication status and whether they recommended the continued use of the medication given that day. Finally, a clinical team made recommendations for treatment taking into account each child's individual response. RESULTS Both drugs were routinely superior to placebo and produced dramatic improvements in rates of negative behavior, academic productivity, and staff/parent ratings of behavior. The doses of Adderall that were assessed produced greater improvement than did the assessed doses of Ritalin, particularly the lower dose of Ritalin, on numerous but not all measures. This result suggests that the doses of Adderall used were functionally more potent than those for Ritalin. Adderall was generally superior to the low dose of Ritalin when the effects of Ritalin were wearing off at midday and late afternoon/early evening. The lower dose of Adderall produced effects comparable to those of the higher dose of Ritalin. Both drugs produced low and comparable levels of clinically significant side effects. Staff clinical recommendations for continued medication favored Adderall three to one. Almost 25% of the study participants were judged to be nonresponders by the clinical team, presumably because of their large beneficial response to the concurrent behavioral intervention and minimal incremental benefit from medication. CONCLUSIONS This is the first investigation to assess comparable doses of Adderall and Ritalin directly. (ABSTRACT TRU