Naive T lymphocytes maintain a quiescent resting state until they encounter antigen whereupon they undergo a switch in their metabolic program in preparation for proliferation and differentiation. This activation process involves a dramatic upregulation of protein synthesis that is essential for cell growth and the differentiation of effector function. An essential regulator of protein synthesis in T cells is the mammalian target of rapamycin (mTOR), a serine/threonine kinase that regulates both the availability of amino acids and the process of cap-dependent translation. Recent data indicate that mTOR influences activation and cell fate determination in T cells. We discuss these findings in light of what is currently known about the function of mTOR and its targets in CD8 T cells.