The purpose of the study - the study of the prevalence of multiple sclerosis (MS) in the Altai Territory. During the period from 1996 to 2009, it collected information on patients with definite MS living in the Altai Territory. On 01.01.2010, the prevalence of MS in the Altai Territory was 39.9 per 100 thousand. Population (standardized prevalence in the European population - 36.9 per 100 thousand.). Thus, the Altai region belongs to the zone of average risk of developing MS. What design of the study was