This chapter contains sections titled: Introduction The clinical questions How are aPL measured in the laboratory? How is APS diagnosed? What is the value of LA, aCL, and anti‐β2‐GPI assays in the evaluation of patients with suspected APS? What is the optimal management of patients with aPL? What is the optimal management of patients with aPL without thrombosis? What is the optimal management of patients with aPL and venous thromboembolism? What is the optimal management of patients with aPL and arterial thromboembolism? What is the optimal management of patients with aPL and recurrent thrombosis? What is the optimal management of women with aPL and pregnancy morbidity? References Introduction The clinical questions How are aPL measured in the laboratory? How is APS diagnosed? What is the value of LA, aCL, and anti‐β2‐GPI assays in the evaluation of patients with suspected APS? What is the optimal management of patients with aPL? What is the optimal management of patients with aPL without thrombosis? What is the optimal management of patients with aPL and venous thromboembolism? What is the optimal management of patients with aPL and arterial thromboembolism? What is the optimal management of patients with aPL and recurrent thrombosis? What is the optimal management of women with aPL and pregnancy morbidity? References