With the development of tests to detect infection with Human Immunodeficiency Virus (HIV), it has become possible to determine its prevalence and to monitor trends in populations. Such information is valuable in designing, implementing, and monitoring public health programs for the prevention and control of HIV and the Acquired Immune Deficiency Syndrome (AIDS). Before the screening of any population for HIV infection, a variety of logistic, laboratory, operational, legal, and ethical issues must be carefully considered. The design of a methodology for HIV surveillance should attempt to maximize the likelihood of obtaining accurate and useful epidemiological information about the distribution of HIV infection in the community concerned while minimizing the likelihood of adverse consequences. Each surveillance method has its limitations. Over the last few years, however, epidemiologists have increasingly advocated unlinked anonymous screening as an accurate and cost-effective method for public health surveillance of HIV infection. The main objective of the European Meeting on HIV Seropositivity and AIDS Prevention and Control was to determine how and when surveys of HIV seropositivity could be used, by reviewing their epidemiological, psychosocial, ethical and legal aspects. Such surveys would be integral components of national AIDS prevention and control programs. This report includes discussion and recommendations on the methods, problems, and usefulness of testing, on ethical and practical issues of HIV surveillance, and the scope and characteristics of effective national programs. (LLL)