More than a decade has gone by since the detailed clinical description of antiphospholipid syndrome (APS). Thrombosis, the main complication of the syndrome, can affect vessels of all sizes; the consistent histopathologic lesion is a bland thrombus without inflammation. Animal models are providing important new data on clinical and pathogenic aspects of APS. New data on the biology of the so-called cofactor beta 2-glycoprotein I is now available. Clearly, the mode of presentation of the phospholipid antigen appears significant, and beta 2-glycoprotein I may play an important part. Regarding treatment, there is further confirmation that long-term anticoagulation therapy with maintenance of a high international normalized ratio is needed in patients with antiphospholipid antibody-associated thrombosis to prevent recurrences.