It is now 10 years since the first AIDS cases were reported in the USA. In that relatively short period of time, study of the disease has moved from the level of early clinical description to exhaustive and extensive laboratory characterization of the human immunodeficiency virus (HIV), the immune responses directed towards it and reasons for their failure. This volume provides contributions from clinical and basic scientists who are actively involved in research in a number of areas of current interest and controversy. Further progress in the clinical management of the HIV-infected patient will undoubtedly build on the basic knowledge about HIV and its modes of pathogenesis. The intimate relationship between HIV and the human immune system provides observations and questions that are relevant to viral immunopathogenesis in general. In the first chapter the clinical features of HIV immunodeficiency are re­ viewed, and aspects of its changing face are discussed. Dr Tersmette then presents evidence for changing viral characteristics at different stages of the disease. This view of close competition for ascendancy between HIV and the host immune response raises questions about current approaches to therapy.