Expression of the T-cell receptor (TCR) was investigated on peripheral lymphocytes in 270 samples from HIV+ patients at different stages of infection. TCR is composed either of an alpha and a beta chain, or, in a smaller subset of T-cells, of a gamma and a delta chain, closely associated with CD3. The numbers and percentages of positive cells were established using monoclonals to the alpha and delta chains of TCR. The values of alpha-TCR positive cells were constantly lower than those observed for CD3, with a mean of 53% (+/- 19%) versus 66% (+/- 17) respectively for asymptomatic patients or patients with persistent generalized lymphadenopathy, and of 36% (+/- 19) versus 46% (+/- 21) for patients with AIDS disease. There was no compensatory increase in the number of cells expressing delta-TCR. These data demonstrate a new alteration of the immune system in HIV infection, which appears to occur early in this disease.