To summarize knowledge about attention deficit disorder in the areas of epidemiology, etiology, clinical predictors, assessments, natural history and outcome, and management. A literature review of articles, books, and chapters primarily published in the past 10 years was completed. Articles presenting new information, most relevant to clinical practice, were reviewed. Key findings in the areas listed above are presented. Major advances have been made in all areas. The clinical picture has been refined and developmental manifestations have been delineated. Patterns of comorbidity have been detailed. Various etiological factors, particularly in the biological area, have been investigated. Multimodal management has been promulgated as the treatment of choice.