Antiphospholipid syndrome (APS) is a clinical condition that has not been well defined yet. Although the clinical component is well established, the laboratory part is a mood issue. According to current guidelines, 3 tests (lupus anticoagulant, anticardiolipin, and anti β2-glycoprotein I antibodies) are officially recommended to assess the presence of antiphospholipid antibodies. According to test positivity, patients are classified into categories in clinical studies. However, it is now clear that classification categories have a different impact on the clinical course of APS. Indeed, patients and healthy carriers with a full positive antibody profile (triple positivity) are those at the highest risk of events. Patients with a single test positivity are those at a lower risk. In this review, on the basis of a laboratory profile, we grade the diagnosis of APS into definite, probable/possible, and uncertain. We also discuss secondary prevention of thrombotic APS, prevention of pregnancy morbidity, and treatment of catastrophic APS. Finally, new tools in laboratory diagnosis and treatment are highlighted.