Anti-double stranded (ds) DNA antibody is an autoantibody specific for systemic lupus erythematosus (SLE). For the measurement of this antibody, radioimmunoassay (RIA) or enzyme-linked immunosorbent assay (ELISA) is widely used in Japan. We studied the correlation of anti-dsDNA levels in 158 sera from 53 SLE patients between RIA and ELISA. The correlation coefficient between anti-dsDNA antibody levels measured by RIA and ELISA was 0.736 (p < 0.001). The concordance rate of sera with both ELISA/RIA-positive or both ELISA/RIA-negative results was 82.3% (130/158 sera). Twenty sera (12.7%) of 14 patients were ELISA-positive but RIA-positive, and 8 sera (5.0%) of 6 patients were ELISA-negative but RIA-positive. Our results suggest that both methods may be equally reliable for the detection of anti-dsDNA antibodies and that ELISA may be more sensitive than RIA. ELISA may be preferable because of its simplicity and convenience of the measurement procedure. The correlation coefficient between anti-ssDNA levels measured by ELISA and anti-dsDNA levels measured by RIA was 0.322 (p < 0.01), and the correlation coefficient between anti-ssDNA and anti-dsDNA antibody levels measured by ELISA was slightly higher, 0.515 (p < 0.001). These results may reflect the predominance of anti-DNA antibodies reactive with both ss and dsDNA in SLE sera. Since the clinical significance of anti-ssDNA antibodies remains unclear, further analysis of accumulated cases is required.