OBJECTIVE: It is estimated that childhood attention deficit hyperactivity disorder (ADHD) remits by adulthood in approximately 50% of cases; however, this conclusion is typically based on single endpoints, failing to consider longitudinal patterns of ADHD expression. The authors investigated the extent to which children with ADHD experience recovery and variable patterns of remission by adulthood. METHODS: Children with ADHD (N=558) in the Multimodal Treatment Study of ADHD (MTA) underwent eight assessments over follow-ups ranging from 2 years (mean age, 10.44 years) to 16 years (mean age, 25.12 years) after baseline. The authors identified participants with fully remitted, partially remitted, and persistent ADHD at each time point on the basis of parent, teacher, and self-reports of ADHD symptoms and impairment, treatment utilization, and substance use and mental disorders. Longitudinal patterns of remission and persistence were identified that considered context and timing. RESULTS: Approximately 30% of children with ADHD experienced full remission at some point during the follow-up period; however, a majority of them (60%) experienced recurrence of ADHD after the initial period of remission. Only 9.1% of the sample demonstrated recovery (sustained remission) by study endpoint, and only 10.8% demonstrated stable ADHD persistence across study time points. Most participants with ADHD (63.8%) had fluctuating periods of remission and recurrence over time. CONCLUSIONS: The MTA findings challenge the notion that approximately 50% of children with ADHD outgrow the disorder by adulthood. Most cases demonstrated fluctuating symptoms between childhood and young adulthood. Although intermittent periods of remission can be expected in most cases, 90% of children with ADHD in MTA continued to experience residual symptoms into young adulthood.