Multiple sclerosis (MS) is a chronic, inflammatory, autoimmune disease of the central nervous system (CNS) of unknown aetiology. It affects mostly young adults and is characterised by multifocal and temporally scattered CNS damage of varied symptomatology and clinical course, eventually leading to significant motor impairment. Studies of the natural course of MS provide valuable data on the course of the disease in individual stages of multiple sclerosis. They allow to determine the frequency of relapses, duration of remission and, most importantly, to determine the motor disability increase rate and describe demographic and clinical factors of influence on benign or aggressive course of the disease. Data on the subject come mostly from four patient databases (Lyon; London, Ontario; Gothenburg; Vancouver) including from several hundred to five thousand patients. The results obtained from hitherto conducted analyses are often non-uniform. Peak MS morbidity dates between 20 and 39 years of age. In primary progressive multiple sclerosis (PPMS) patients, the disease onset occurs on average 10 years later than in relapsing-remitting multiple sclerosis (RRMS) patients. The initial symptoms have monosymptomatic character in over 75% of patients. Pyramid signs are the most important predictive factor for clinically definite multiple sclerosis (CDMS) development after a clinically isolated syndrome (CIS) episode. The conversion of RRMS to secondary progressive multiple sclerosis (SPMS) occurs on average 10 years after onset of the disease. Significant motor disability develops after 15-20 years of multiple sclerosis, the strongest adverse prognostic factor is PPMS.