An interview schedule was used to record the personality traits of 130 psychiatric patients, 65 with a primary clinical diagnosis of personality disorder and 65 with other diagnoses. The results were analysed by factor analysis and three types of cluster analysis. Factor analysis showed a similar structure of personality variables in both groups of patients, supporting the notion that personality disorders differ only in degree from the personalities of other psychiatric patients. Cluster analysis revealed five discrete categories; sociopathic, passive-dependent, anankastic, schizoid and a non-personality-disordered group. Of all the personality-disordered patients 63 per cent fell into the passive-dependent or sociopathic category. The results suggest that the current classification of personality disorder could be simplified.