The development of a questionnaire to be completed by parents for use in screening preschool children is described. Ninety per cent of children attending a psychiatric clinic were identified when the criteria were a score of 11 or more points on the behaviour scale and/or inability to speak in 3-word phrases, and/or speech which was very difficult to understand. The questionnaire could be used as a basis for collecting information systematically about preschool children, and as a screening device for identifying children with behaviour difficulties and developmental delay.