Central memory CD8⁺ T cells (T_CM) and effector memory CD8⁺ T cells (T_EM) are found in humans and mice; however, their relative contributions to host immunity have only recently been examined in vivo. Further, the ability of T_CM to treat an established tumor or infection has yet to be evaluated. To address the therapeutic potential of different tumor-reactive CD8⁺ T cell memory subsets, we used an established model for the in vitro generation of T_CM and T_EM by using IL-15 and IL-2, respectively. Adoptively transferred T_CM exhibited a potent in vivo recall response when combined with tumor-antigen vaccination and exogenous IL-2, leading to the eradication of large established tumors. By contrast, T_EM were far less effective on a per-cell basis. Microarray analysis revealed that the signature of highly in vivo effective antitumor T cells included the overexpression of genes responsible for trafficking to secondary lymphoid tissues. This gene expression profile correctly predicted the in vitro and in vivo lymphoid-homing attributes of tumor-reactive T cells. Furthermore, we found that homing to secondary lymphoid tissue is required for optimal tumor treatment. Our findings indicated that highly in vivo effective antitumor T cells were those that initially targeted secondary lymphoid tissue, rather than tumor sites, as had previously been postulated. Thus, tumor-reactive CD8⁺ T cell populations with the phenotypic and functional attributes of T_CM may be superior to T_EM/effector T cells for adoptive immunotherapies using concomitant tumor-antigen vaccination.