The importance of the subjective response in the clinical use of certain drugs is such that, the staff of the anesthesia laboratory of the Harvard Medical School has for some years been interested in the quantitative evaluation of these responses in the necessary experimental animal, man. Certain agents of considerable interest in pharmacology, such as amphetamine, may be used primarily to alter mood. On the other hand, mood changes present limiting factors in the use of some drugs (e. g., euphoria and addiction liability in analgesics or dysphoria as an undesirable side-effect of any drug). We have found, in studying drug effects of this kind, that a combination of self-scoring questionnaires and interrogation is most successful in eliciting subjective responses from young, intelligent, healthy male volunteer subjects. In a pilot study of nine such subjects, the results obtained with morphine, heroin, and amphetamine were considerably at variance with textbook descriptions.