It was suggested by Gibson & Curran (1974) that the rather complex relationships found to obtain between hypnotic susceptibility and the personality parameters of extraversion and neuroticism might be understood by considering neuroticism as a moderator variable (as had been suggested by Furneaux & Gibson, 1961). They made the hypothesis that if a tranquillizing drug were administered the operative level of neuroticism would be decreased, and as a consequence the level of susceptibility of neurotic extraverts would be raised, and that of neurotic introverts lowered. This study reports the test-retest data on a sample of 71 subjects on the Stanford Hypnotic Susceptibility Scales, half of whom were retested with diazepam and half with nicotinic acid. The hypothesis was confirmed and additional data are given on the drug/placebo effects on each item of the scale. The significance of drugs on different aspects of hypnotic susceptibility in relation to personality is discussed.