Myelin reactive T cells are considered to play an important role in the pathogenesis of Multiple Sclerosis (MS). This is partially based on observations in the animal model of MS, experimental autoimmune encephalomyelitis (EAE), that myelin reactive T cells can transfer the disease to native rodents. Recent data in EAE suggest that encephalitogenic and non-encephalitogenic myelin reactive T cells differ with respect to their cytokine secretion profile: pathogenic myelin reactive T cells express a Th1 phenotype, while non-pathogenic T cells preferentially produce Th2 cytokines. To study whether similar subsets can be identified in human myelin reactive T cells, the cytokine profile of a panel of myelin basic protein reactive T cell clones from MS patients and control subjects was evaluated. Most of the MBP reactive clones expressed pro-inflammatory cytokines, but did not show a clearly defined Th1 phenotype. In this paper current data on the cytokine profile of murine and human myelin reactive T cells from our laboratory and other groups will be reviewed. The relevance of these findings with respect to the pathogenesis and possible cytokine based therapies in MS will be discussed.