35 patients with Behcet's disease (BD) were examined for antiphospholipid antibodies (aPL). Elevated levels of antibodies to cardiolipin (aCL) were registered in 20% of the patients (aCL IgG and IgM in 11.4 and 8.6%, respectively). Low positivity of these antibodies prevailed (33.2 GPL and 41.2 MPL). Lupus anticoagulant was present in 6 patients. No distinct correlation was found between positivity by aPL and vascular disorders. It is inferred that aPL do not seem to play a leading role in thrombotic diathesis in BD. This diathesis is brought by a much more complicated and multifactor process.