We analysed MR examinations of 227 patients with multiple sclerosis. White matter hyperintensities in brain were found in 270 of them. The most frequently they were found in periventricular white matter (in 100% of cases), in subcortical localization (52.2%) and in the corpus collosum (44.4%). MR examination allows to estimate the activity of the disease on the basis of the presence of oedema around the plaques and their contrast enhancement with gadopentetate dimeglumine (Gd-DTPA). 17.8% of all cases showed the signs of the acute phase of MS. About one-third of all cases were accompanied by cortical brain atrophy (the most often seen in frontal lobes), subcortical brain atrophy was less frequent (one-sixth). In about two-third of all casese the corpus callosum atrophy was found. The analysis of follow-up MR examinations of 83 patients taking part in a double-blind placebo-controlled trial of new immunosupressive drug cladribine showed that patients from pacebo group were more compliant to any changes of plaques. Decrease of the plaques size was found mainly in women. No correlation between patients age and the plaques changes was established.