Venous thromboembolism is being increasingly diagnosed in neonates and is the result of a disturbance of the delicate balance between procoagulant and anticoagulant factors in neonatal blood. The primary risk factors are the use of central venous catheters, and prematurity. The contribution of maternal risk factors and the role of inherited thrombophilias is poorly understood. Because the evidence for treatment is absent or of low quality, treatment recommendations (the CHEST guidelines) are based on consensus and expert opinion. The anticoagulants most often used are unfractionated heparin and low-molecular weight heparin. Thrombolytics (tissue plasminogen activator and others) carry significant risks, and are not recommended unless the thrombosis threatens life, limb or organs.