The physiological and psychological changes throughout the day subsequent to the administration of Lysergic Acid Diethyl-amide were recorded and analyses made of their interrelations. The Harvard Polygraph was used to simultaneously and continuously record heart rate, respiration, skin temperature, blood pressure, and muscle tension. Recordings were made under resting conditions immediately before and 1½, 2½, 4½, and 7½ hours subsequent to L. S. D. administration.Physiologically, a general sympathetic excitation resulted, which reached a peak of tension in 3 to 4 hours and then gradually returned to the pre-L. S. D. level by the eighth hour. Heart rate increased and became more stable, systolic and diastolic blood pressures were elevated, pulse pressure rose, muscle tension mounted, skin temperature tended to drop, breathing became faster and more variable, the inspiration/respiration ratio decreased and became more variable, and pupillary dilation occurred. No such drastic changes were noted in the control (placebo) days.Changes occurred psychologically that paralleled the physiological changes. Deviation from "normality" both behaviorally and subjectively was most pronounced, in number of symptoms expressed and intensity of expression, about 3 to 4 hours after L. S. D. administration and gradually diminished until the eighth hour.Some of the implications of this study are mentioned and the similarity between the sequences of events post-L. S. D. with the changes pre-post lobotomy are discussed.