A population study of 409 seven-year-old children in a middle-sized Swedish town was performed. All children were examined by the same doctor and evaluated by means of parent interview, motor examinations, and teacher reports on behaviour in the classroom. Follow-up was carried out 8 months later. The rate of severe problems in the fields of attention deficit-hyperactivity disorder (ADHD), developmental coordination disorder (DCD), and deficits in attention, motor control, and perception (DAMP) (the combination of ADHD and DCD) was 6.1%, with boys being affected more frequently than girls. There was considerable overlap between ADHD and DCD, with about half of each diagnostic group also meeting criteria for the other diagnosis. Attention deficits at diagnosis strongly predicted attention deficits at follow-up. If parents had noted attention deficits in the home setting, then teachers almost always independently agreed that there were similar problems in the classroom. However, the reverse did not always apply. Clumsiness also showed striking stability over time. The diagnosis of DAMP, particularly severe DAMP, had a stronger association with classroom dysfunction and with high Conners scores than did diagnoses of ADHD or DCD. It is concluded that DAMP may be a clinically valid diagnostic construct.