Worldwide, the majority of human immunodeficiency virus–1 cases occur through heterosexual transmission, yet little is known regarding the phenotype of CD4⁺ T cells in the vaginal mucosa. In the present study, lymphocytes were compared from the lymph nodes, blood, and vagina from uninfected and simian immunodeficiency virus (SIV)–infected macaques. In mature female macaques, 54%–67% of the vaginal CD4⁺ T cells expressed C chemokine receptor 5 (CCR5), whereas 84%–99% coexpressed CXC chemokine receptor 4. In contrast, only 4.4%–14.8% of peripheral blood and 2.4%–13% of lymph-node CD4⁺ T cells coexpressed CCR5. Moreover, CCR5 mean channel fluorescence was significantly higher on CD4 cells from the vagina, compared with those from blood. In macaques intravenously infected with SIV, rapid depletion of CD4⁺ T cells was observed in the vagina, particularly among the CCR5⁺CD4⁺ subset. This demonstrates that large numbers of CD4⁺ T cells expressing high levels of CCR5 reside within the vagina and that these cells are preferentially targeted for elimination by SIV infection