As a result of recent therapeutic trials, recombinant Interferon beta (rIFN beta)-Ib and -Ia as well as Copolymer I (COP I) and to some extent unspecific immunosuppressants have been accepted as partially efficient treatments of relapsing-remitting MS. In view of partially effective single treatments, the question arises if combination of two or even more-agents could improve efficacy without increasing side effects. The theoretical background of possible combinations is discussed. The selection of combination partners should be based on their proven efficacy as single treatment, on their mode of action and their distinct target in the pathogenetic cascade of events and on their specific side effect profile. Combination regimens selected in this way should undergo evaluation in short term early phase II studies and if the results are positive enter phase III studies. The use of surrogate markers (especially MRI-findings) may help to accelerate this process. Combinations that could enter phase II and III studies in the near future are rIFN beta with unspecific immunosuppressants, e.g. Azathioprine or Methotrexate and rIFN beta with COP I. Combinations including agents just entering phase I and II studies as a single treatment may be more promising for the future.