This issue of Hematology Oncology Clinics of North America is dedicated to the topic of Antiphospholipid Syndromes. The antiphospholipid syndromes are the most common of the acquired thrombophilias, yet remain unclear and confusing to most clinicians and physicians in general. These disorders commonly lead to arterial and venous thrombosis and other serious clinical sequealae, but many physicians forget to consider testing for antiphospholipid syndrome when faced with these events. Indeed many do not recognize the different antiphospholipid antibodies that may lead to thrombotic and thromboembolic events and other catastrophic events in a wide variety of medical and surgical settings. Thus this issue is written by experts in these various specialties wherein antiphospholipid syndromes are most commonly seen. In addition sections are dedicated to laboratory diagnostic features and tests available, pathophysiology and controversies.