Numerous investigators have reported impressive improvement rates when LSD has been used as an aid to ongoing psychotherapy, but absence of controls makes these findings difficult to evaluate. In the present study, 21 psychosomatic inpatients and 7 nonpsychotic psychiatric inpatients were randomly assigned to two psychotherapy groups, one of which received five LSD sessions and a second which received five placebo drug sessions during the course of psychotherapy. Patients in both groups were seen twice weekly over a period of 13 weeks for psychotherapy interviews in addition to the drug sessions. As measured by a number of self-report devices and clinical ratings there were no differential effects of treatment, as both groups improved to a modest extent. Twenty of the patients, equally divided between the LSD and the control groups, were followed up after 18 months. At this point the few differences found between the LSD and placebo group favored the latter. The placebo group was more emotionally stable, conscientious, and more socially precise than the LSD group according to self-report measures. There was a tendency for scores on both groups' self-report measures to regress to their pretreatment levels. According to clinical ratings, the gains in level of adjustment shown at post-treatment were maintained at the 18-month follow-up period regardless of the type of treatment received. The results and clinical impressions suggest that LSD is of minimal value as an adjunct in the treatment of marginally motivated and psychologically unsophisticated individuals.