CD11b, CD11c, and F4/80 are normally used to define dendritic cell and/or macrophage populations. In this study, the expression of all three markers was observed on CD8(+) T cells following infection of mice with several distinct viruses. Using lymphocytic choriomeningitis virus as a model virus, it was found that relatively more CD11b(+)CD8(+) and CD11c(+)CD8(+) T cells were present in the periphery than in primary lymphoid organs; in contrast, the F4/80(+)CD8(+) T cell population was more prevalent in the spleen. All three myeloid markers were detected on virus-specific CTL. The expression of CD11b and CD11c on CD8(+) T cells correlated with their level of CTL activity, whereas the F4/80(+)CD8(+) T cell population increased after the peak of the CTL response but did not have higher CTL activity. These data suggest that there is a differential induction of CD11b, CD11c, and F4/80 on virus-specific CD8(+) T cells following an acute virus infection.