We determined whether positive ANA was related to response to rIFNss-1a in 62 relapsing-remitting MS patients. According to the presence of antinuclear antibodies (ANA) at baseline and during the first 6 months of treatment, patients were sorted in different groups. The clinical and MRI outcome during short-term (6 months) and long-term (24 months) treatment period was not statistically different between the groups. Therefore, the response to IFNbeta-1a seems not to be influenced by ANA occurrence either before or during treatment. When the analysis was extended to other autoantibodies (i. e. antithyroid, anticardiolipin) similar results were obtained.