The occurrence of autoantibodies is a common feature of autoimmune diseases. This review is intended to give an overview of the most important autoantibodies and their role in diagnosis, disease activity and prognosis in rheumatoid arthritis (RA), systemic lupus erythematodes (SLE) and multiple sclerosis (MS). Whereas in RA and SLE these antibodies are meaningful for diagnosis and partially for the prognosis of the disease, the situation is quite different in the case of MS. Up to date, no specific antibody is known to be exclusively present in the serum or cerebrospinal fluid (CSF) of MS-patients compared to the respective fluids of healthy individuals. Nevertheless, there are some antigens that are reported to be bound significantly more often by MS-patients' serum or CSF than by comparable samples of healthy volunteers. In addition to the importance of several autoantibodies for diagnosis of the respective disease, the serum concentration of certain antibodies in RA and SLE is associated with therapy response. Since therapy with biologicals (e.g. TNF- αblockade, B-cell depletion) is expensive, monitoring these autoantibodies seems to be an additional useful tool for early identification of therapy responders or non-responders.