Ever since IFN-beta1b was first approved for the treatment of relapsing-remitting multiple sclerosis (RRMS) in the US and Europe, other disease-modifying drugs have become available. Phase III clinical trials have shown the efficacy of IFN-beta1b in the treatment of RRMS and secondary progressive MS in that it can reduce the annual relapse rate as well as magnetic resonance imaging parameters of activity and progression. There is mounting evidence that the best time to initiate treatment is early in the course of the disease, and available data suggest that efficacy is sustained for at least 5 years. IFN-beta1b is safe and well tolerated, although there are adverse events such as the flu-like complex and skin reactions. In the face of a proportion of RRMS patients experiencing a poor response to the drug, other therapeutic approaches need to be considered.