• Various methods that might be used in testing the effects of a new drug on physical and mental activity were tried in three experiments. In the first, the subjects knew what drug (pipradrol) and what dosage they were taking; they recorded their own impressions, and their behavior was noted by observers; thus both subjects and observers became familiar with the stimulating effects of the drug. In the second experiment, each of eight subjects determined for himself the dosage he believed had sufficiently marked effects for him to recognize and was then tested for his ability to tell the drug from a placebo in a set of unknowns; the observers were similarly tested for their ability to recognize the behavioral effects of the drug. Half of the subjects and observers were correct in all their evaluations. This experiment gave the investigators further opportunity to learn about and correct for erroneous discriminations because of placebo reactions or other false criteria of drug effect. In the third experiment, seven of the subjects participating in experiment 2 were again tested as to their ability to distinguish the drug (in individually chosen dosage) from the placebo, and observers were tested for their ability to tell, by any desired objective criteria, whether the subject was taking drug or placebo. The responses of the subjects were correct in 47 out of 60 trials, and the reports of the observers were correct in 45 out of 60 trials. The authors believe that there are advantages in using trained subjects such as psychiatrists, psychologists, and pharmacologists in experiments involving the psychological effects of drugs and that samples of writing and speech lend themselves well to objective analysis for determining psychopharmacological reactions. Pipradrol, taken by mouth in single doses of from 2 to 6 mg., increased psychological and motor activity. Whether such an effect was manifested at this dosage, however, depended to some extent on the typical personality of the subject before taking the drug.