Interferon beta (IFN-beta) is generally considered an effective treatment for multiple sclerosis (MS). Importance of binding antibodies (BAb), which are created during the treatment of MS by the use of IFN-beta, hasn't been completely explained, however it is generally reckoned that they might be one of the factors diminishing treatment efficacy. The aim of the study was the appreciation of BAb occurrence during the treatment of MS by the use of different types of interferon beta and their impact on clinical efficacy. The study included 47 patients with relapsing-remitting MS. Within 24 months 37 patients were given two different preparations of IFN-beta 1-a and 10 patients were given IFN-beta 1-b. Every 6 months clinical parameters and BAb level in serum by EIA method were estimated. All preparations of IFN-beta induced appearance of BAb, but frequency of developing BAb to IFN-beta varied according to the IFN beta given. The high levels of BAb appeared significant frequently in patients treated with IFN-beta 1-b than in patients treated with both preparations of IFN-beta 1-a. After 2 years of treatment greater disability, measured by EDSS scale was encountered in patients with high levels of BAb but differences weren't statistically significant. As well, it wasn't stated significant correlation between exacerbation numbers during the treatment.