The mind-body connection is well-established and evidence is mounting for a connection between stress, decreased immune function and tumor development. The studies described herein investigated the effects of the glucocorticoid hormone, corticosterone (CORT), on the function of tumor-antigen specific CD8 T cells. K11 cells are a clonal CD8 T cell line specific for epitope I of the Simian Virus 40 large tumor antigen (Tag) protein. Tag is a known oncoprotein that induces transformation of cells in vitro and tumor formation in susceptible animals. Control of Tag-induced tumors in vivo is mediated largely by CD8 T cells specific for Tag. Treatment of K11 cells with physiologically relevant levels of CORT decreased their expansion during co-culture with Tag-expressing target cells. IFN-γ production by the K11 cells was also markedly decreased. In contrast, the ability of K11 cells to lyse Tag-expressing target cells was unaffected by CORT treatment. Ultimately, these studies will enhance our understanding of the mechanism(s) whereby stress hormones alter a tumor-specific immune response in vivo.