Th17 cells are quite recently discovered subpopulation of T helper lymphocytes, characterized by the production of IL-17 (IL-17). Research on these lymphocytes gives new light on the pathogenesis of multiple sclerosis (MS) and its experimental model (EAE). These lymphocytes have a high similarity to Th1 cells and naïve T CD4+ differentiate into Th17 phenotype under the influence of a specific set of cytokines. Formation of murine Th17 cells is induced by cytokines TGF-β and IL-6 or IL-21. Th17 cells produce various chemokines, including IL-17A/F, IL-21 and IL-22. It has been documented that the neutralization of IL-17 reduces the symptoms of the disease in an animal model of MS. The main mediator of central nervous system (CNS) pathology induced by Th17 cells is IL-17A. One of the best characterized function of IL-17A is the induction of the production of neutrophilic CXC ELR+ chemokines: CXCL1 and CXCL2. Moreover, Th17 cells can promote the development of EAE by activation of neutrophils within the bone marrow, which in consequences leads to the mobilization of immature monocytes into the bloodstream and the development of inflammation in the CNS. A growing number of data from the studies on MS and EAE confirms a major role of Th17 lymphocytes in the pathogenesis of this disease. Understanding the exact role of these cells requires further studies, since their results may be useful in developing new therapies for MS.