Antiphospholipid antibodies (APA) have been described not only in systemic lupus erythematosus but also in several inflammatory diseases of the connective tissue, some infections, neoplasms, in pregnancy and even in apparently healthy individuals. Arterial and venous thrombosis are some of the clinical manifestations most frequently associated with APA. Two patients with ankylosing spondylitis with antiphospholipid antibodies are presented. The first patient developed a infarct in the pons as a complication at 34 years of age, with high titres of anticardiolipin antibodies as the only factor predisposing a cerebral vascular accident. The second patient had deep vein thrombosis with the presence of circulating anticoagulant. These are the first cases of antiphospholipid syndrome associated to ankylosing spondylitis in the literature.