The problem of acquired immune deficiency syndrome (AIDS) in Europe and public health measures that can be taken to reduce the spread of infection are discussed. These guidelines cover: the magnitude of the problem in Europe, the virus and its mode of transmission, major clinical features of the disease, laboratory tests, possibilities of treatment and prophylaxis, the role of blood and blood products, the public health importance of the disease, and control measures. In addition to considering preventing the spread of infection to the general population, attention is directed to prevention for groups with increased risk of infection and hospital staff and health care workers. Data up to September 30, 1985 are incorporated for 21 European countries, including: the total number of AIDs cases in the countries and estimated rates per million population; AIDs cases by patient risk group and geographic origin; AIDs cases by disease category and number of deaths; and AIDS cases by age group and sex. Functions of a World Health Organization collaborating center for AIDS are also identified. Appendices include the case definition of AIDs used by the U.S. Centers for Disease Control (CDC) for national reporting, and a list of participants in the Consultation on AIDs Policies in Europe, which was held at CDC in April 1985. (SW)