Human immunodeficiency virus (HIV) types 1 and 2 infect cells of the immune system and initiate a robust immune response which counteracts the viral spread but also accelerates the destruction of the immune system. Many pathogenic mechanisms have been proposed which include viral gene products, syncytium formation, direct virus killing of cells, apoptosis, autoimmunity, cytokine and chemokine expression, superantigens, virus directed cell-mediated cytolysis, and disruption of the lymphoid architecture. At present, there is no unifying theory or experimental proof of a single or a predominant mechanism for the pathogenesis of the HIV disease. This review is intended to highlight areas of HIV research relevant to the understanding of HIV immunopathogenesis.