This is a report of a study designed to measure personality, attitude, value, interest, and performance changes resulting from the administration of LSD to normals. Several investigators using LSD with humans in nontherapy experiments have observed that some of their subjects report various lasting effects attributable to the drug experience. 1 -2 In addition, the recent controversy over the nonmedical use of LSD has given rise to numerous claims and counterclaims in this regard. We have previously reported on a pilot study in which tests of anxiety, attitudes, and creativity were given to 15 subjects prior to, and one week following, a single 200 microgram LSD session. Some significant changes in the anxiety and attitude tests were observed, but none were found for the creativity measures. 3 The assessment of lasting effects of hallucinogens involves extradrug variables to a greater extent than do most drug studies. We are asking, in effect, whether a dramatic drug-induced experience-one which temporarily dissolves the primacy of habitual perceptions of self image, environment, beliefs, and values-will have a lasting impact on the individual's personality. We would expect any such impact to be influenced by the person's prior personality, motivation, and expectation, and by 1. Reprinted with permission from Archives of General