Introduction— Multiple sclerosis (MS) is an autoimmune disorder, but an unique antigen has not been found. Antiganglioside antibodies (AGA) have been reported in MS, nevertheless, a clinical significance of AGA in MS has not been established. The aims of this study were to study AGA in sera of MS patients and to investigate relationships between AGA and clinical course of MS. Material and methods— 42 patients with MS who fulfilled the criteria of clinically definite disease (59% RRMS, 21% SPMS, 20% PPMS), 89 patients with systemic lupus erythematosus and 36 healthy controls were studied. A modification of previously described ELISA techniques was used to estimate serum IgG and IgM anti-GM1, asialoGM1 and anti-GDla antibodies. Results— 47.6% of the patients showed AGA reactivity. Anti-GM1 was found in 38% of MS patients, anti-asialoGM1 in 23.8% and anti-GDla in 33.3%. IgG was the isotype more commonly found. A correlation between presence of AGA and progressive disease and between anti-GDla and PPMS was found. Conclusions— The presence of AGA in MS patients is elevated. In contrast with the results of others authors, a strong correlation between AGA and progressive disease is showed in our study.