A questionnaire concerned with expected effects of marihuana was completed by 182 persons with histories of social use of the drug. The majority of subjects were relatively infrequent users. Reported experiences from use were greater among the most frequent users, and included some unpleasant effects. Five factors of marihuana expectations were derived pertaining to: functional interference, euphoria, psychological distress, perceptual alteration and psychotomimetic effects. These results clearly suggest that the marihuana effect is multidimensional and that the profile of response differs from one individual to another. Studies of marihuana effects under various experimental conditions should take the nature of the effects as well as their magnitudes into consideration. The results also suggest that the marihuana questionnaire can be used to determine in advance the expectations of individual experimental subjects and thus to control for effects of set on responses in experimental studies of marihuana. One should thus be able to settle the question of the extent to which different expectations about marihuana produce variability in responses of subjects in experimental studies of effects of the drug.