Venous thromboembolism is a common and potentially life-threatening complication that occurs in 4 to 15% of patients admitted to ICUs despite the routine use of pharmacological prophylaxis. We therefore recommend an institution-wide protocol for the prevention of venous thromboembolism (Grade 1B). The routine use of ultrasonographic screening for deep vein thrombosis is not recommended when thromboprophylactic measures are in place (Grade 1B), as the detection of asymptomatic deep vein thrombosis may prompt therapeutic anticoagulation that may increase bleeding risk but has no proven reduction of clinically significant thrombotic events. In critically ill patients, we recommend pharmacological prophylaxis with low molecular weight heparin over low-dose heparin (Grade 1B). For critically ill patients with severe renal insufficiency, we suggest the use of low-dose heparin (Grade 2C), dalteparin (Grade 2B) or reduced doses of enoxaparin (Grade 2C). Monitoring of anti-Xa activity may be considered when low molecular weight heparin is used in these patients (Grade 2C). No study has prospectively evaluated the efficacy and safety of deep vein thrombosis prophylaxis in critically ill patients with severe liver dysfunction. Thus, the use of pharmacological prophylaxis in these patients should be carefully balanced against the risk of bleeding. For critically ill patients, we recommend against the routine use of inferior vena cava filters for the primary prevention of venous thromboembolism (Grade 1C). When the diagnosis of heparin-induced thrombocytopaenia is suspected or confirmed, all forms of heparin must be discontinued (Grade 1B). In these patients, immediate anticoagulation with a nonheparin anticoagulant rather than discontinuation of heparin alone is recommended (Grade 1C).