Epidemiological data concerning multiple sclerosis (MS) and collected by roughly the same methods in the regions of Rostock (GDR) and Schumadija-Pomoravlje (Yugoslavia) are presented. In both regions the females were earlier and more frequently attacked than the males; possible genetic, etiopathogenetic and other factors are discussed. The age at which the disease becomes manifest is about the same in both regions and was 30.9 and 30.8 years respectively. A prevalence of 60.4 and an incidence of 2.9 per 100 000 inhabitants were calculated for the Rostock region. The corresponding data for the Yugoslavian region were 20.3 (prevalence) and 0.89 (incidence). The disease is more common among the urban than among the rural population in Yugoslavia; the comparison of mortality due to MS revealed no appreciable differences.