Less than 1% of patients with the antiphospholipid antibody syndrome (APS) can develop multiple, simultaneous organ-system thromboembolic disease, which is referred to as the catastrophic antiphospholipid antibody syndrome (CAPS). Roughly one-half of these patients have systemic lupus erythematosus (SLE). Factors known to precipitate CAPS include infection, surgery, trauma, neoplasia, anticoagulation withdrawal, obstetric complications, and SLE flares. Optimal treatment includes anticoagulation and high-dose corticosteroids, although IVIG and plasma exchange may also have a role. The overall mortality of CAPS is roughly 50%, but prompt clinical recognition of this rare but devastating syndrome may lead to improved outcomes.