Apolipoprotein E plays an important role in metabolism of cholesterol and in modulation of inflammatory reaction, processes of significance in pathology of multiple sclerosis. Therefore great interest is noted in the impact of ApoE on the pathophysiology of multiple sclerosis. The role of APOE as a gene associated with incidence of multiple sclerosis was a subject of many studies. The basic question whether a particular genotype of APOE or presence of particular alleles is predisposing the host to development of multiple sclerosis received till now no positive answer. The relatively high frequency of APOE genotype in multiple sclerosis patients did not reach statistical significance. Also the results demonstrating the influence of particular APOE genotypes or alleles on development of multiple sclerosis subgroups (relapsing-remitting form or primarily progressing form) proved to be insignificant and the association between the APOE alleles and frequency of relapses was not definitely established. The positive correlation was noted only in individual studies. The association between APOE allele and intensified progression of multiple sclerosis seems to be established. Most important were the results demonstrating an association between APOE ε4 and rapid disease progression in studies using magnetic resonance imaging but the apolipoprotein E genotype was not directly associated with severity of the disease, tested using the multiple sclerosis severity scale. The presence of APOE ε4 allele as a factor predisposing for development of cognitive deficit in multiple sclerosis, especially in learning and recent memory, seems to be well documented. The severe cognitive deficit in victims of multiple sclerosis was evidently associated with the ε4 allele and promotor polymorphism. It was even linked to a five-fold increase in the relative risk of cognitive impairment. The results obtained in Polish population were identical.