We have previously shown preferential tumor-homing and therapeutic efficacy of adoptively transferred type 1 CTL (Tc1) when compared with type 2 CTL (Tc2) in mice bearing intracranial ovalbumin-transfected melanoma (M05). Further characterizing the expression of a panel of homing receptors on Tc1 and Tc2 cells, we found that very late antigen (VLA)-4 (a heterodimer of CD49d and CD29), but none of other receptors evaluated, was expressed at significantly higher levels on Tc1 cells than on Tc2 cells. Although CD49d (α₄ integrin) can form heterodimers with both β₁ (CD29) and β₇ integrins, α₄β₇ complexes were not expressed by either Tc1 or Tc2 cells, suggesting that CD49d is solely expressed in VLA-4 complexes. VLA-4 expression on Tc2 cells was down-regulated in an interleukin (IL)-4 dose-dependent manner but not by other type 2 cytokines, such as IL-10 and IL-13, suggesting that IL-4 uniquely down-regulates VLA-4 expression on these cells. In accordance with the differential expression of VLA-4 on Tc1 versus Tc2 cells, Tc1 cells alone were competent to adhere to plate-bound VCAM-1-Ig fusion protein. Finally, the efficient trafficking of Tc1 cells into intracranial M05 lesions in vivo was efficiently blocked by administration of monoclonal antibodies against CD49d or VCAM-1 or small interfering RNA–mediated silencing of CD49d on Tc1 cells. Collectively, these data support the critical role of VLA-4 in the effective intracranial tumor homing of adoptive-transferred, antigen-specific Tc1 cells and suggest that more effective vaccine and/or ex vivo T-cell activation regimens may be developed by promoting the generation of VLA-4⁺ antitumor Tc1 cells. [Cancer Res 2007;67(13):6451–8]