This is a study of the psychology of college students who are heavy and habitual users of marijuana.Fifteen students who used marijuana regularly and heavily were studied in detail using psychoanalytic interviewing techniques. Short term therapy was administered when indicated. Psychological tests (Wechsler Adult Intelligence Scale, Rorschach, Thematic Apperception Test, Sentence Completion, Figure Drawing, and Word Association) were performed and used as an independent check on the data derived from the interviews. An equal number of students who used marijuana only occasionally were also studied.Psychiatric studies of marijuana abuse among students have centered around the question of whether marijuana causes changes in attitudes toward achievement, ambition, and competition, or whether it is merely an accompaniment of a change in values and life style. This study indicates that neither view is accurate and describes the specific role marijuana plays for students with problems related to competition, aggression, and achievement.