Since the original description and definition of the antiphospholipid syndrome (APS), a number of distinct clinical manifestations related to it have appeared in the literature. These include vascular obstruction of both veins and arteries, thrombus formation on the endocardium and its consequences, as well as a group of other conditions where vascular obstructive mechanisms are either incompletely understood or unproven, eg, chorea, avascular necrosis, and pulmonary hypertension. Single vessel (large/medium) involvement or multiple vascular occlusions may cause a wide variety of presentations. Any combination of vascular occlusive events may occur in the same individual, and the time interval between them also varies considerably from weeks to months or even years. Rapid chronological occlusive events occurring over days to weeks have been termed the "catastrophic" APS. Most of these complications may be ascribed to the hypercoagulable state of which antiphospholipid antibodies appear either to be "markers" or intimately connected with the highly complex coagulation mechanisms resulting in thrombotic occlusions.