In a patient with liver cirrhosis, an elevation of serum anti-dsDNA antibody titer (100-193.3 IU/ml) measured by Farr method was found. This anti-dsDNA antibody was not identified by Crithidia Luciliae method, and the analysis using ELISA method showed that the DNA-antibody is an anti-ssDNA antibody (IgG) and that it is reactive only with ssDNA by the suppression test using purified DNA with lambda phage. Based on this finding, the high titer of anti-dsDNA antibody found in this patient using Farr method was considered to be non-specific cross-reaction with ssDNA.