Although the clinical manifestations and neuropathological signs of multiple sclerosis (MS) have been known for a century, the cause of this disease has not yet been determined. The epidemiological studies indicate that MS is of multifactorial etiology, including both environmental and inherited (genetic predisposition) factors. The role of the HLA system in genetic predisposition to MS has been known since the 1970s. As a result of the progress made in human genetics, it is now possible to study genetic predisposition to MS.