Minutes on the fourth annual conference contain reports on AIDS from participating countries and an overview of research projects in the United States. An article then reports on the nature and effectiveness of a type of drug-user needle exchange program in a number of European countries. It involves the use of 24-hour vending machines that dispense sterile needles. Such programs are designed to reduce the risk of AIDS from using infected needles to inject drugs. A brief report on the needle exchange program used by a clinic and social service agency in Portland, Ore., provides statistics on the number of clients, return visits, syringes dispensed, and syringes returned. A report on investigator-initiated research programs sponsored by the National Institute on Drug Abuse focuses on research pertaining to the progression of disease among intravenous drug user relative to that observed in other populations and the effectiveness of AIDS prevention strategies among intravenous drug users. The supplement provides summaries of presentations on drug use and AIDS.