Objective: To review the primary and secondary findings from the Multimodal Treatment study of ADHD (MTA) published over the past decade as three sets of articles. Method: In a two-part article--Part I: Executive Summary (without distracting details) and Part II: Supporting Details (with additional background and detail required by the complexity of the MTA)--we address confusion and controversy about the findings. Results: We discuss the basic features of the gold standard used to produce scientific evidence, the randomized clinical trial, for which was used to contrast four treatment conditions: medication management alone (MedMgt), behavior therapy alone (Beh), the combination of these two (Comb), and a community comparison of treatment "as usual" (CC). For each of the three assessment points we review three areas that we believe are important for appreciation of the findings: definition of evidence from the MTA, interpretation of the serial presentations of findings at each assessment point with a different definition of long-term, and qualification of the interim conclusions about long-term effects of treatments for ADHD. Conclusion: We discuss the possible clinical relevance of the MTA and present some practical suggestions based on current knowledge and uncertainties facing families, clinicians, and investigators regarding the long-term use of stimulant medication and behavioral therapy in the treatment of children with ADHD. [For Part II: "Supporting Details," see EJ798028.]