BackgroundIn the face of rapidly expanding empirical knowledge about this common childhood condition, there is a need for an up-to-date synthesis, especially for the use of practising clinicians.MethodThe main epidemiological, experimental and clinical studies over the past decade are selectively reviewed.ResultsHyperkinetic/attention deficit hyperactivity disorder is common, with young school-age males most frequently affected. The prevalence figures vary depending on the criteria used. Overlap with conduct disorder is high. The causes are likely to stem from a combination of biological, often genetically determined neurochemical disturbances, and environmental disadvantages, with the biological risk tending to be highest in severely hyperactive girls. Good clinical management combines pharmacological, psychological and educational approaches in a sustained manner. Even then, the outcome is often equivocal and the long-term psychosocial adaptation unpredictable.ConclusionsClinically significant hyperactivity is rooted in biological, often genetically transmitted vulnerabilities, upon which environmental disadvantages transact. It may be viewed as a disorder of self-regulation with its roots partly in strained early caregiver–child interactions and disrupted primary attachments.