Brenman and Gill state that approximately between seventy-eight and ninety-seven per cent of the total population can be hypnotized to some degree, but that only about twenty per cent can be deeply hypnotized. In their experience, hysterics are not particularly susceptible to hypnosis. The only way one can determine hypnotizability is to try to hypnotize the patient. There does not seem to be a correlation between the depth of hypnosis and the therapeutic results. The determining factor seems to be the extent to which the patient permits himself deep emotional participation in his hypnotic experiences. The dangers connected with the use of hypnotherapy seem to have been unduly exaggerated. The only specific contraindication is the presence of strong paranoid ideas. The authors conclude that hypnosis is a powerful and dangerous tool and should only be used by trained psychotherapists who will apply it within the solid framework of their theoretical understanding and clinical experience.