Stimulant medications have proven to be effective in reducing the core symptoms of hyperactivity, impulsivity and inattention and are considered the first line of therapy for patients with attention-deficit/hyperactivity disorder (ADHD). Mixed amphetamine salts extended-release capsules (MAS XR; Adderall XR, Shire Pharmaceuticals Group) include immediate-release pellets of mixed amphetamine salts that release the first half of the dose upon ingestion and delayed-release pellets that begin to release active drug approximately 4 h later. The MAS XR capsule contains the same 3:1 ratio of dextroamphetamine to levoamphetamine as do mixed amphetamine salts immediate-release tablets (MAS IR; Adderall), Shire Pharmaceuticals Group), and the bioavailability and pharmacokinetic profiles of MAS XR 20 mg are comparable to those with MAS IR 10 mg b.i.d. MAS XR has a rapid onset of action--within 1.5 h--and provides 12 h coverage. The efficacy, safety and extended duration of action of MAS XR have been established through clinical studies in school-age children, adolescents and adults.