Chlorpromazine hydrochloride (3-chloro-10 (3′-dimethylamino-propyl)-phenothiazine) or “largactil” is being widely tried out as a form of therapy in psychiatric disorders. Papers have appeared describing its use in comparatively severe conditions encountered in in-patient mental hospital practice (e.g. Anton-Stephens, 1954) and in psychoneurotics (e.g. Garmany, May and Folkson, 1954). In the psychoneurotic group in particular, the drug is reported to be helpful in reducing tension and diminishing pre-occupation with worries, fears, and concomitant symptoms. These two properties—the reduction of tension and the production of a feeling of relative indifference to distressing stimuli—were amongst those originally attributed to chlorpromazine by Sigwald and Bouttier (1953) and, of course, they approximate to the characteristic changes resulting from prefrontal leucotomy (Partridge, 1950). The effects of this operative procedure have been extensively studied in relationship to such factors as the previous personality of the patient and the duration of the illness involved (e.g. Baker and Minski, 1951) and it was considered that it might be of value to investigate similar factors in patients treated with chlorpromazine. It is true that prefrontal leucotomy entails structural damage as a result of which the previous personality, for example, may be expected to have a significant bearing on the therapeutic outcome, but even with patients treated by chlorpromazine the ultimate result may depend, at least to some extent, on the inherent make-up of the individual or the symptom-complex from which he is suffering. It was in order to study the relationship between factors of this nature and chlorpromazine treatment that the following investigation was undertaken.