This proposal is for a randomized, controlled clinical trial comparing the efficacy of combining interferon-beta (IFN) with glatiramer acetate (GA) to treat relapsing forms of multiple sclerosis (MS). At present, both IFN and GA are available, individually, for treatment of relapsing forms of MS. Pivotal trials combining agents have not yet been performed, although this approach would offer the hope of improving upon the modest efficacy results obtained in clinical trials of the agents individually. Further, there are no properly randomized, controlled studies comparing the efficacy of IFN to GA. This trial will allow for a comparison of the relative efficacy of each agent alone and in combination against the better of the single agents. As these are expensive therapies and the results of the agents alone are modest, it is of great importance to develop better therapeutic modalities. There is currently only one new agent in phase III testing for relapsing MS; thus, combination therapy is the best hope of improving treatment options for patients with relapsing MS. The trial design to be employed will serve as a standard for comparing and combining any of the therapeutic agents for treatment of MS and will provide longer-term data than any prior controlled MS trial.