The antiphospholipid syndrome (APS) is characterized by the association of antiphospholipid antibodies with venous and/or arterial thrombosis, recurrent abortions and thrombocytopenia. With respect to this latter clinical manifestation, a variable degree of thrombocytopenia occurs in approximately 20-40% of the patients with APS, it is generally mild and does not modify the policy for treatment of thrombosis. Severe thrombocytopenia is relatively uncommon and seldom associated with bleeding complications. When required, its treatment is similar to that of idiopathic thrombocytopenic purpura. Finally, uncertainties still exist as to the interaction between aPL antibodies and platelets and to the role of platelets and these antibodies on the pathogenesis of the thrombotic complications of the APS.