Details are given of an open-ended interview schedule designed to obtain a full description from a parent of a child's behavioural abnormalities. After spontaneous complaints have been aired, the parent is asked systematically a series of 36 questions covering all areas in which symptoms commonly occur. Results of preliminary use of the schedule involving interviews with 268 parents suggest that the reliability of the overall judgment of psychiatric abnormality is high. The reliability of rating individual symptoms was also high where strict behavioural criteria could be met, but items where inferences had to be drawn or where relationships were being judged proved less satisfactory. When parents were interviewed on two separate occasions, the amount and type of spontaneous complaint varied considerably on the two occasions. The advantages of the systematic approach in obtaining adequate information for diagnostic purposes seem overwhelming, and it is suggested that this part of the schedule may have value in both clinical and research work in child psychiatric disorder.