There is evidence that the presence of antiphospholipid antibodies is related with an increased risk of thrombotic events. Patients with definite antiphospholipid syndrome (APS) and a first venous event should receive long term oral anticoagulation to an international normalized ratio (INR) of 2.0-3.0. In patients with definite APS and arterial or recurrent thrombosis oral anticoagulation to an INR > 3.0 may be advisable. Catastrophic antiphospholipid syndrome is an unusual form of presentation of antiphospholipid syndrome with a mortality rate of approximately 50%. Its treatment is based on the combined use of full anticoagulation, corticosteroids, plasma exchanges, and intravenous immunoglobulins. We also summarize the evidence-based information about management of some difficult cases such as “seronegative” APS and patients who do not display formal classification criteria for APS.