Psychiatrists differentiate types of abnormal personality in practice by assigning a descriptive label to indicate the chief way in which the patient's behaviour deviates from what is usual in society. The use by psychiatrists of such a category system for diagnosing abnormal personality has been discussed in two previous papers (Walton et al., 1970; Walton and Presly, 1973). The diagnostic system evaluated was one which included categories contained in the American Psychiatric Association classification (1968) and in the relevant section of the International Classification of Diseases (1965).