This paper deals with the difficulties which acting out presents in the psycho-analysis of psychopathic and delinquent patients. The author has found that these patients are only capable of a narcissistic infantile type of relationship in which the patient feels himself to be part of the analyst. This can only be replaced by a more advanced object relationship, by a consistent analysis of the narcissistic defence as it presents in the analysis. Any interpretations which threaten the patient's narcissism are likely to precipitate episodes of acting out. The counter-transference reactions of the analyst are of greater importance in the treatment of such patients than in the psychoneurotic reactions.