Psychiatrists have responded to the challenge of abandoning the adjective ‘psychopathic’ in current disease classification systems. This paper nevertheless advocates caution in the application of the consequent diagnostic criteria. Comorbidity — the presence of two or more diseases at the same time — may be as indicative of confusion as of extensive pathology. Furthermore, the diagnoses of most interest (because of their association with repeated violence or other antisocial behaviour) show poor agreement between people using the instrument for measuring them, and poor stability over time. However, studies support the existence of a relatively distinct group, broadly referred to as erratic or flamboyant, who are often dangerous and for whom the short‐term prognosis is poor. Much more work is needed to improve the clarity of diagnosis of personality disorders.