Laboratoire d'Hygi'ene de la Facult'e de M'edecine de Lyon Universit'e Claude-Bernard, Domaine Rockefeller, 8, avenue Rockefeller, 69373 Lyon Cedex 2 France.

The objective of this study was to investigate the false-positive reactions in the Kline, FTA200 and FTA-ABS tests in acute disseminated lupus erythematosus, polyarthritis and controls. Though the false-positive Kline tests are frequent in autoimmune diseases, false-positive FTA200 when made on non lyophilised treponema are uncommon. On the other hand, when lyophilised treponema are used as substrate for the immunofluorescence, false-positive FTA200 and FTA-ABS are more common in the patients with autoimmune diseases than in controls. The false-positives had two patterns of fluorescence "beaded" or "homogeneous". The present investigation suggests that the false-positive reactions of the beaded type are due to the presence of anti-DNA antibodies in the sera.