Peptide-major histocompatibility complex class I (pMHC-I) tetramers have been an invaluable tool to study CD8(+) T-cell responses. Because these reagents directly bind to T-cell receptors on the surface of CD8(+) T-lymphocytes, fluorochrome-labeled pMHC-I tetramers enable the accurate detection of antigen (Ag)-specific CD8(+) T-cells without the need for in vitro re-stimulation. Moreover, when combined with multi-color flow cytometry, pMHC-I tetramer staining can reveal key aspects of Ag-specific CD8(+) T-cells, including differentiation stage, memory phenotype, and activation status. These types of analyses have been especially useful in the field of HIV immunology where CD8(+) T-cells can affect progression to AIDS. Experimental infection of rhesus macaques with simian immunodeficiency virus (SIV) provides an invaluable tool to study cellular immunity against the AIDS virus. As a result, considerable progress has been made in defining and characterizing T-cell responses in this animal model. Here we present an optimized protocol for enumerating SIV-specific CD8(+) T-cells in rhesus macaques by pMHC-I tetramer staining. Our assay permits the simultaneous quantification and memory phenotyping of two pMHC-I tetramer+ CD8(+) T-cell populations per test, which might be useful for tracking SIV-specific CD8(+) T-cell responses generated by vaccination or SIV infection. Considering the relevance of nonhuman primates in biomedical research, this methodology is applicable for studying CD8(+) T-cell responses in multiple disease settings.