Normal volunteers were successfully hypnotized using a videotape induction technique. EEG measurements were made before trance induction, during induction, and during objective testing of the depth of hypnosis. Electronic analysis of EEG records revealed a significant correlation between hypnotizability and certain EEG patterns, including the presence of very fast activity. During the trance-induction and trance-testing periods, good hypnotic subjects showed a significant decrease in slow activity and an increase in alpha and beta waves. In later experiments, such psychotropic drugs as LSD-25 and dextroamphetamine were found to alter hypnotizability.