part of the time. The role relationship between the experimenters and the patients was naturally quite different from the role relationship between the experimenters and the professional volunteer Ss. When a professional volunteer takes LSD in the presence of a colleague he is frequently thrown into considerable conflict as to what his role should be. This often presents a rather difficult situation for the person who is administering the drug as well. In describing the effects that we have observed under these conditions and with these Ss, it is important to distinguish between two classes of effects. One class is the immediate effects, i.e., those which occur within eight to twelve hours after ingestion of the drug. The other class consists of the more lasting effects, i.e., those which persist for an indeterminate period after the immediate effects have dissipated. In studying the immediate effects, the approach has been to observe the subject's relatively spontaneous behavior while he is under the influence of the drug and also to analyze the tape recordings made of each drug session. Effects The immediate effects which have been observed can roughly be classified into five categories: 1) Mood and affect; 2) Interpersonal behavior; 3) Sensory and perceptual effects; 4) Intellectual functioning and reality testing; 5) Intuitive-intellectual effects. In terms of mood and affect, Ss have demonstrated a wide range of reactions. Often an emotional lability is seen which ranges from tearfulness to euphoria. There is frequently an increased intensity to emotions in general. Feelings