ABSTRACTIntroduction:Lisdexamfetamine dimesylate (LDX), a prodrug stimulant, is indicated for attention-deficit/hyperactivity disorder (ADHD) in children 6–12 years of age and in adults. In shortterm studies, once-daily LDX provided efficacy throughout the day. This study presented here was conducted to assess the long-term safety, tolerability, and effectiveness of LDX in 6- to 12-year-olds with ADHD.Methods:This open-label, multicenter, singlearm study enrolled children with Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition-Text Revision criteria for ADHD. Following 1-week screening and washout periods, subjects were titrated to LDX 30, 50, or 70 mg/day over 4 weeks and placed on maintenance treatment for 11 months. The ADHD Rating Scale and Clinical Global Impression-Improvement scale measured effectiveness.Results:Of 272 subjects receiving LDX, 147 completed the study. Most adverse events were mild to moderate and occurred during the first 4 weeks. There were no clinically meaningful changes in blood pressure or electrocardiographic parameters. From baseline to endpoint, mean ADHD Rating Scale scores improved by 27.2 points (P<.0001). Improvements occurred during each of the first 4 weeks, and were maintained throughout. Based on Clinical Global Impression-Improvement scale scores, >80% of subjects at endpoint and >95% of completers at 12 months were rated “improved.”Conclusion:Long-term 30, 50, and 70 mg/day LDX was generally well tolerated and effective in children with ADHD.