This paper attempts to construct a simplified system for the classification of personality disorders, and relates this system to normally distributed human personality characteristics. One hundred and forty-eight subjects with a variety of psychiatric diagnoses were evaluated using the SCID-II structured clinical interview for personality disorders. A four-factor solution of personality disorder symptoms was obtained and we labelled these factors ‘the four As’ : antisocial, asocial, asthenic and anankastic. The factors related to the four temperament dimensions of the Tridimensional Personality Questionnaire (TPQ), but less closely to Eysenck Personality Questionnaire (EPQ) dimensions. The four factors were similar to those identified in a number of studies using a variety of assessment methods and this lends some credibility to our findings. It suggests that a more parsimonious set of trait descriptors could be used to provide simpler, less overlapping categories that retain links with current clinical practice. In addition, these factors can be seen as extremes of normally distributed behaviours obtained using the TPQ questionnaire.