Nine pregnant women with false-positive syphilis test results, and 13 matched controls, were screened for autoimmune antibodies to ascertain whether any relationship might exist between their presence and the occurrence of obstetric problems. Investigations included assays for anti-cardiolipin antibodies (ACA), lupus anticoagulant (LAC), anti-nuclear antibodies (ANA) (including antibodies against extractable nuclear antigen), anti-smooth muscle antibodies, anti-mitochondrial antibodies, anti-DNA antibodies, IgM-RF and complement factors. We found no significant difference in the incidence of obstetric problems between the two groups. Except that significantly more women were positive for ACA in the group with false-positive syphilis tests than in the control group, there were no differences between the groups with regard to the antibodies tested for. There was only one case of SLE, a patient positive for LAC, and who had had several miscarriages and no pregnancy resulting in a live birth. Our findings suggest that it would be unwarranted to devote resources to routine screening for these antibodies in healthy women with a false-positive syphilis test result, though the presence of LAC could possibly be used as an indicator of the risk of spontaneous abortion due to SLE.