The worldwide impact of infection with human immunodeficiency virus type 1 (HIV- is reflected in the cumulative number ofHIV- 1 infections, which is now predicted to exceed 40 million by the year 2000---equivalent to the n- ber of humans who perished in World War II. The medical and scientific - sponse to the HIV-1 pandemic has steadily grown since its recognition in 1981. The outlay by the United States alone for HIV research funded by the National Institutes of Health in 1997 was $1. 4 billion. Laboratory-based HIV research has brought together academic clinicians, retrovirologists, molecular biologists, and immunologists in the formation of research teams attempting to dissect the viral and host factors contributing to disease pathogenesis. Increasing focus is being placed on those aspects of viral biology and host immune responses that bear on the development of vaccines to prevent HIV infection. HIVProtocols reflects the state of HIV research in several ways. First, chapters are organized into four sections: Virology, Molecular Biology, Humoral Immunology, and Cellular Immunology. This organization is a natural consequence of the diverse scientific disciplines that have been attracted to HIV research. Second, the chapters reflect such diverse research directions as viral coreceptor usage, quantitation of viral genomes, HIV promoter function, B-cell epitope mapping, and measurements of T-cell function, each of which bears on the goal of understanding the viral and host immune responses that will be critical to the design of effective preventive vaccines.