In order to determine the role of CD4+ T cells and CD8+ T cells in causing antigen-induced eosinophil infiltration into the site of late-phase reaction (LPR), we examined the effect of the in vivo depletion of CD4+ T cells and CD8+ T cells on antigen-induced eosinophil infiltration into mouse skin. Eosinophil infiltration into the skin of ovalbumin (OA)-sensitized BALB/c mice was biphasic after subcutaneous OA challenge, reaching the first peak at 6 h and the second peak at 24 to 48 h. The in vivo depletion of CD4+ T cells by pretreatment with anti-L3T4 monoclonal antibody (mAb) significantly decreased the second peak (at 24 h and 48 h), but not the first peak (at 6 h), of OA-induced eosinophil infiltration into the skin of OA-sensitized mice. However, the depletion of CD8+ T cells by pretreatment with anti-Lyt-2 mAb had no significant effect on either the first or second peak of OA-induced cutaneous eosinophilia in the mouse. These results indicate that CD4+ T cells, but not CD8+ T cells, play an important role in causing antigen-induced eosinophil recruitment of cutaneous LPR.