Investigation into the nature and treatment of emotional disorders in children requires reliable and valid measuring instruments. The Children's Pathology Index is described. It consists of 38 five-item categories and may be administered in 20 to 30 minutes by child-care staff. Little training is required, results from four raters are pooled and raters may be changed on subsequent occasions. Factor analysis yields four factors I) Disturbed Behaviour Towards Adults; II) Neurotic Constriction; III) Destructive Behaviour; IV) Disturbed Self Perception. Results demonstrate satisfactory reliability for all four factors and adequate validity studies have been made for Factor I. The subjects were boys and girls aged 6–12 years, of different diagnostic categories, most of whom were admitted because of acting out behaviour disorders. Comments are made on the usefulness of Factor I estimates in assessing social acceptability of children whatever the other difficulties present or the diagnosis made.