An expansion of CD8+ lymphocytes associated with a monoclonal rearrangement of the T-cell receptor gamma locus was found in a woman with HIV-1 infection. A subpopulation of HIV-positive patients display an unusual response to HIV infection characterized by a persistent marked CD8+ lymphocytosis, the presence of which appears to be associated with an improved long-term prognosis. This condition is thought to represent a florid immune response to an ongoing viral infection which may be HIV itself, and suggests that monoclonal proliferation of CD8+ lymphocytes does not imply the presence of an underlying malignant process.