The preliminary results of a post-marketing study on relapsing-remitting multiple sclerosis patients treated with immunomodulating agents attending the Lombardia Region's Multiple Sclerosis Centers are presented. A total of 294 patients treated with Betaferon (67), Avonex (115), Rebif 22 (45), Rebif 44 (18) and Copaxone (49) were included. Relapse frequency consistently decreases at 1 year and continues to decrease after 5 years of treatment, without differences between therapeutic groups. Eighty-seven out of 294 patients (29.6%) discontinued treatment for different reasons. Forty-eight of them shifted to a second therapeutic agent. A different trend, to lower or higher doses of interferon or immunosuppression, according to reasons of discontinuation, was observed.