Since January 2020, Elsevier has established a COVID-19 resource center on Elsevier Connect, providing free information in English and Mandarin about the novel coronavirus. The company has granted permission to make all COVID-19-related research available in PubMed Central and other public repositories, with unrestricted access for research reuse and analysis. The article discusses the coagulation abnormalities and thrombosis observed in patients with COVID-19. While most patients have a respiratory tract infection, a significant proportion progress to severe systemic disease, characterized by treatment-resistant fever, acute lung injury, shock, and multiple organ dysfunction. Coagulopathy in these patients is associated with an increased risk of death and can lead to venous and arterial thromboembolic complications. Key findings include elevated D-dimer concentrations, mild thrombocytopenia, and prolonged prothrombin time. These abnormalities are distinct from those seen in disseminated intravascular coagulation (DIC) and thrombotic microangiopathy. The coagulopathy is a combination of low-grade DIC and localized pulmonary thrombotic microangiopathy, which can significantly impact organ dysfunction. Severe COVID-19 is also linked to increased concentrations of proinflammatory cytokines, which can induce tissue factor expression and activate coagulation. The fibrinolytic system is activated, and there is a potential for hypercoagulability, increasing the risk of thromboembolic complications. Prophylactic low molecular weight heparin (LMWH) is suggested for critically ill patients to prevent venous thromboembolism. Further research is needed to confirm the effectiveness of such treatments.Since January 2020, Elsevier has established a COVID-19 resource center on Elsevier Connect, providing free information in English and Mandarin about the novel coronavirus. The company has granted permission to make all COVID-19-related research available in PubMed Central and other public repositories, with unrestricted access for research reuse and analysis. The article discusses the coagulation abnormalities and thrombosis observed in patients with COVID-19. While most patients have a respiratory tract infection, a significant proportion progress to severe systemic disease, characterized by treatment-resistant fever, acute lung injury, shock, and multiple organ dysfunction. Coagulopathy in these patients is associated with an increased risk of death and can lead to venous and arterial thromboembolic complications. Key findings include elevated D-dimer concentrations, mild thrombocytopenia, and prolonged prothrombin time. These abnormalities are distinct from those seen in disseminated intravascular coagulation (DIC) and thrombotic microangiopathy. The coagulopathy is a combination of low-grade DIC and localized pulmonary thrombotic microangiopathy, which can significantly impact organ dysfunction. Severe COVID-19 is also linked to increased concentrations of proinflammatory cytokines, which can induce tissue factor expression and activate coagulation. The fibrinolytic system is activated, and there is a potential for hypercoagulability, increasing the risk of thromboembolic complications. Prophylactic low molecular weight heparin (LMWH) is suggested for critically ill patients to prevent venous thromboembolism. Further research is needed to confirm the effectiveness of such treatments.