Types of “hyperkinetic syndrome” were studied using data from the general population epidemiological study of 10-to 11-year-olds on the Isle of Wight who were followed up at 14–15 years old. Characteristics of situationally hyperactive children were compared with those of pervasively hyperactive children, as defined in terms of the hyperactivity factor scores on the Rimer parent and teacher questionnaires. The association of situational hyperactivity with general emotional/behavioural disturbance was a nonspecific Ending; situational unsociability was also related to disturbance. In contrast, pervasive hyperactivity, a clinically distinctive behaviour pattern, was strongly associated with general behavioural disturbance, persistence of overall disorder and marked cognitive impairment. These findings indicate the importance of identifying the type of hyperactivity.