The autoantibody test gives significant information for diagnosis of autoimmune diseases. Since the finding of the LE-cell in 1948, dozens of autoantibodies have been found. Anti nuclear antibody (ANA) is the essential test for the screening of autoantibodies. Indirect immunofluorescence (IIF) is the conventional method for the detection of ANA. IIF can detect a wide spectrum of ANA and gives abundant information obtained from a staining pattern. However under the recent circumstances of using advanced fluorescent microscopes and reagents we often have difficulty interpreting positive results seen in normal individuals and in detailed staining patterns. ELISA (enzyme-linked immunosorbent assay), detecting disease specific autoantibodies alone, is one solution. Some antibodies such as anti-DNA or anti-ENA (extractable nuclear antigen) have a strong relation to specific diseases. These autoantibodies have been detected by IIF, RIA (radioimmunoassay) or DID (double immune diffusion). With the progress of molecular biology many autoantigens have been characterized. Now ELISA is a typical way to detect autoantibodies because purified or recombinant antigens are easily available. Though RF (rheumatoid factor) is the historical autoantibody detected in RA patients, the specificity to RA is low. The new anti-CCP is promising from its high specificity and sensitivity. Now we can choose various kind of autoantibody tests, not only conventional ones but also newly developed ones. For diagnosis and treatment of autoimmune diseases, understanding of both clinical significance and methodology is important.