In all, 1872 children were recruited as part of a larger study concerning food additives and behaviours in preschool children. This figure represented 70% of the whole population of 3 1/4 -year-old children resident on the Isle of Wight, UK. Parents completed an assessment concerning their perceptions of their child's behaviour. The results of this assessment were compared with scores on two validated parental questionnaires, the Weiss Werry Peters (WWP) hyperactivity scale and the Emotionality, Activity and Sociability Temperament Questionnaire (EAS), which were used to assess hyperactivity. The accuracy of parents in perceiving hyperactivity in their children was found to be around 50% if the child was hyperactive, and 89% if the child was not hyperactive. The implications of these findings for services are discussed. Frequencies of potential risk groups for future Attention Deficit Hyperactivity Disorder (ADHD) and Conduct Disorder were also suggested.