Induction of adaptive immunity to human immunodeficiency virus type 1 (HIV-1) at the mucosal site of transmission is poorly understood but crucial in devising strategies to control and prevent infection. To gain further understanding of HIV-1-specific T-cell mucosal immunity, we established HIV-1-specific CD8؉ cytotoxic T-lymphocyte (CTL) cell lines and clones from the blood, cervix, rectum, and semen of 12 HIV-1-infected individuals and compared their specificities, cytolytic function, and T-cell receptor (TCR) clonotypes. Blood and mucosal CD8؉ CTL had common HIV-1 epitope specificities and major histocompatibility complex restriction patterns. Moreover, both systemic and mucosal CTL lysed targets with similar efficiency, primarily through the perforin-dependent pathway in in vitro studies. Sequence analysis of the TCR VDJ region revealed in some cases identical HIV-1-specific CTL clones in different compartments in the same HIV-1-infected individual. These results clearly establish that a subset of blood and mucosal HIV-1-specific CTL can have a common origin and can traffic between anatomically distinct compartments. Thus, these effectors can provide immune surveillance at the mucosa, where rapid responses are needed to contain HIV-1 infection.Human immunodeficiency virus type 1 (HIV-1) transmission occurs predominantly within the genital and rectal mucosa through sexual contact. Virus-specific T cells, known to control HIV-1 infection systemically (21, 29, 37), may also facilitate viral clearance in the mucosa. We previously identified class I major histocompatibility complex (MHC)-restricted CD8 ϩ cytotoxic T lymphocytes (CTL) in the cervices of infected women that recognize and lyse HIV-1-infected cells. HIV-1-specific cervical CTL were more frequently detected in patients with preserved rather than decreased CD4 ϩ T-cell counts, suggesting that the CD8 ϩ effectors provide immune surveillance against local viral replication (28). More recently, we and others have extended these findings to semen and the rectal lymphoid tissue of infected men (19,34,38,39).The importance of understanding mechanisms to control infection locally is underscored by recent attention to the distinct properties of HIV-1 within the mucosa. Investigators comparing HIV-1 in blood and mucosal secretions (cervix and semen) have highlighted significant differences in viral phenotypes and genotypes as well as clearance following combination antiretroviral therapy (7,12,20,32,41,43,44). However, although mucosal antibody responses can differ from systemic responses (26), such discrepancies pertaining to HIV-1-specific T cells have not been elucidated. We previously demonstrated that most T cells in the female lower reproductive tract express T-cell receptor ␣ (TCR␣) (15, 28), similar to cells in the circulation and lymph nodes. Nevertheless, it is unclear whether HIV-1-specific CTL in the genital and gastrointestinal tracts emerge distinct from their systemic counterparts. Additionally, it is not known if mucosal CTL, similar to syste...