Grafting T cells with new antigen specificity by T cell receptor (TCR) gene transfer could greatly facilitate adoptive T cell immunotherapy. Little is known about how two TCR on one T cell influence each other. Among other reasons, this is often due to the fact that only one TCR specificity is known. We have genetically generated murine dual TCR T cells (OT-I/P14), specific for ovalbumin(ova257) and lymphocyte choriomeningitis virus glycoprotein (gp33). These cells retain both specificities and can be stimulated by either antigenic peptide to proliferate and produce IFN-gamma. Even though one TCR (P14) is expressed at reduced levels on dual TCR T cells, the peptide sensitivity of these cells is similar to that of single TCR T cells of the same specificity. TCR down-modulation on dual TCR T cells depends primarily on binding of the specific ligand. Adoptively transferred dual TCR T cells suppress the growth of both B16-ova and B16-gp33 melanoma cells, regardless of the peptide used for in vitro activation. Taken together, despite a certain dominance of expression between two TCR on the same T cell, this need not necessarily have functional consequences.