Potential therapeutic strategies in acute ischaemic stroke include reperfusion, prevention of thrombus extension and rethrombosis and neuroprotection. Heparins inhibit thrombin and factor X and therefore may have useful effects on arterial and venous thrombosis; they are effective in the prevention and treatment of deep vein thrombosis (DVT) and pulmonary embolism (PE) and in the prevention of myocardial infarction (MI) in patients with unstable angina. Low molecular weight heparins (LMWHs) and heparinoids are known to be more effective and have a safer profile than unfractionated heparins in patients with venous thromboembolic disease and coronary artery disease. However, their role in acute ischaemic stroke is less clear. The very large International Stroke Trial found that unfractionated heparin had no overall benefit in ischaemic stroke, whilst causing significant intracranial haemorrhage. A number of Phase II and III trials of LMWH have been assessed in acute ischaemic stroke. It remains unclear whether these agents are effective and safe in acute ischaemic stroke although they do reduce the risk of DVT and PE. A systematic review is now required in order to assess the safety and efficacy of LMWH in acute stroke.