Antiphospholipid syndrome (APS) is well known as an autoimmune thrombotic syndrome with recurrent thromboses. In APS, thromboses occurs both artery and vein, and from large to micro vessels. In contrast, so called catastrophic antiphospholipid syndrome, CAPS, develops multiple thromboses at microvessels mainly within a few weeks and induces to poor prognosis. CAPS often occurs in patients with SLE or primary APS after a change of antithrombotic therapy, infection, and operation. Treatments for CAPS have not established although plasma exchange is carried out usually as well as intensive anticoagulation and immunosuppressive therapy. We treated with immunoadsorption plasmapheresis (IAPP) for 5 CAPS patients and they improved their clinical symptoms and ameliorated their titers of antiphospholipid antibodies. IAPP could be an useful treatment skill for CAPS and we have started prospective study.