The aim of the study was to investigate the change of NAA/Cr ratio in the brain parenchyma in patients with MS with the help of protonic multivoxel magnetic resonance spectroscopy (PMMRS) and to detect the correlation between this factor and clinical status of the patients. The study was also performed in order to investigate whether this method can be potentially used for monitoring of the severity of the disease and severity of the neurodegenerative process. On the basis of this knowledge potential neuroprotective effect of the interferon beta 1a (IFN 1а) i.m. (avonex) was investigated. Twenty six patients with relapsing-remitting multiple sclerosis (RRMS) were included in the study. The procedures included examination of the history of the disease, neurological examination, EDSS, neuropsychological tests, dynamic MRI with PMMRS. The decrease of the NAA/Cr ratio in patients with RRMS compared to healthy controls was detected. The dynamic control in a year revealed the decrease NAA/Cr in patients with MS. Negative association was revealed between NAA/Cr in the brain and the level of neurological and cognitive deficit. The analysis of the 1 year therapy with IFN 1а i.m. revealed neuroprotective effect which can be related to the possible positive effect of the drug on the neurodegenaration process.