THE NARROW EPIDEMIOLOGICAL MEDICAL APPROACH IS BASED ON AN ANALOGY BETWEEN HEROIN USE AND INFECTIOUS DISEASE. PROPONENTS OF THIS APPROACH HAVE DEVELOPED A THEORY OF HEROIN ADDICTION BASED ON THE CONTACT BETWEEN SUSCEPTIBLE GROUPS WITH INITIATORS. THE TRIPARTITE BASIS OF DISEASE TRANSMISSION -- HOST, AGENT, ENVIRONMENTAL FACTORS -- IS APPLIED TO THE DIFFUSION OF HEROIN USE. THE PSYCHOSOCIAL MODEL DEFINES HEROIN ADDICTION AS A SPECIAL PROBLEM WITH SOCIETAL, PSYCHOLOGICAL, AND GROUP DETERMINANTS. DRUG ABUSE IS SEEN AS A SYMPTOM OF UNHAPPINESS AND /OR ALIENATION, UNUSUALLY ACCOMPANIED BY PSYCHOPATHOLOGY AND/OR SOCIETAL INADEQUACIES. KEY CONCEPTS OF THE PSYCHOSOCIAL APPROACH ARE STRUCTURALFUNCTIONALISM AND ANXIETY. EPIDEMILOGICAL PERSPECTIVES ON DRUG ABUSE NEED TO BE DEVELOPED WITH GREATER SENSITIVITY TO THE LARGER SOCIAL, PSYCHOLOGICAL, AND POLITICAL ISSUES INVOLVED. A MOVE TO ELIMINATE HEROIN ADDICTION BASED ON THE NARROW EPIDEMIOLOGICAL MODEL WOULD NOT WORK. THE EPIDEMIOLOGICAL PERSPECTIVE IS OF PRIMARY VALUE IN TARGETING SERVICES FOR SPECIFIC GROUPS, NOT IN FORMULATING BROAD PUBLIC POLICY. AS MORE KNOWLEDGE ABOUT THE DIFFUSION OF HEROIN AMONG DIFFERENT POPULATIONS IS GAINED FROM EPIDEMIOLOGICAL STUDIES, A MORE SYSTEMATIZED RELATIONSHIP BETWEEN THE MEDICAL AND PSYCHOSOCIAL MODELS SHOULD DEVELOP. A BIBLIOGRAPHY IS INCLUDED. (LKM)