Various hematological pathologies have been described in association with antiphospholipid syndrome (APS). Thrombocytopenia is frequently found in APS patients, its incidence has ranged from 22-42% in different series, it is usually moderate (>50x10(9)/L) without clinical manifestation and requires no intervention. A high percentage of patients with isolated idiopathic thrombocytopenic purpura have antiphospholipid antibodies, however the pathogenetic role and the clinical importance of these antibodies in this condition is still not clear. Other hematological manifestations reported in association with APS include: bone marrow necrosis, and various thrombotic microangiopathic syndromes such as: thrombotic thrombocytopenic purpura, hemolytic-uremic syndrome, HELLP (hemolysis, elevated liver enzymes, low platelet) syndrome, and catastrophic APS. A high index of suspicion is needed for the early recognition and treatment of these conditions.