In an investigation in the anesthesia laboratory of the Harvard Medical School of mood and other psychological changes induced by a variety of drugs, an opportunity arose to correlate the personality of the subjects involved and the nature of their responses. This was of interest because of the likelihood that the preexisting mental state of a person would affect his psychological responses to drug stimulation. Our results support this assumption and are presented, despite the relatively small number of subjects involved, because of the scarcity of such data in the literature. They indicate profitable areas for further study. METHODS The subjects, drugs, and procedure for eliciting subjective responses are described in a previous paper by us. The volunteers were 20 healthy young males, aged 21 to 27 years, and were, with a few exceptions, college students. Psychological data on each subject consisted of an interview, which lasted from one to