In summary, one can conclude that infected persons exhibit an extremely vigorous, virus-specific CTL response, and in at least some individuals this response is broadly directed at multiple epitopes. These cells are present at the time or initial control of viremia and can also be detected after more than a decade of asymptomatic infection. These cells can also be found in the central nervous system in persons with ADC, and one can envision pathways in which the inflammatory cytokines released by these cells upon activation could contribute to the neurologic sequelae of infection. However, the precise role of these cells as a protective host defense and the possible contribution of these cells, or products released by these cells, to tissue damage at sites such as the lung and brain remain to be determined. Further delineation of the role played by CTLs in the pathogenesis of disease should be extremely useful in helping to understand the disease itself and to guide intervention strategies.