BACKGROUND: Low-molecular-weight heparins and heparinoids are anticoagulants that may be associated with lower risks of haemorrhage and more powerful antithrombotic effects than standard unfractionated heparin. This is an updated version of the original Cochrane review first published in Issue 1, 1995 and previously updated in Issue 2, 2005. OBJECTIVES: To compare the effects of low-molecular-weight heparins or heparinoids with those of unfractionated heparin in people with acute, confirmed or presumed, ischaemic stroke. SEARCH STRATEGY: We searched the Cochrane Stroke Group Trials Register (last searched June 2007). In addition we searched the Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 2, 2007), MEDLINE (1966 to June 2007) and EMBASE (1980 to June 2007). For previous versions of this review we searched MedStrategy (1995) and also contacted pharmaceutical companies. SELECTION CRITERIA: Randomised trials comparing heparinoids or low-molecular-weight heparins with standard unfractionated heparin in people with acute ischaemic stroke. We only included trials where treatment was started within 14 days of stroke onset. DATA COLLECTION AND ANALYSIS: Two review authors independently selected studies for inclusion, assessed trial quality and extracted the data. MAIN RESULTS: Nine trials involving 3137 people were included. Four trials compared a heparinoid (danaparoid), four trials compared low-molecular-weight heparin (enoxaparin or certoparin), and one trial compared an unspecified low-molecular-weight heparin with standard unfractionated heparin. Allocation to low-molecular-weight heparin or heparinoid was associated with a significant reduction in the odds of deep vein thrombosis compared with standard unfractionated heparin (odds ratio (OR) 0.55, 95% confidence interval (CI) 0.44 to 0.70). However, the number of more major events (pulmonary embolism, death, intracranial or extracranial haemorrhage) was too small to provide a reliable estimate of the benefits and risks of low-molecular-weight heparins or heparinoids compared with standard unfractionated heparin for these, arguably more important, outcomes. Insufficient information was available to assess effects on recurrent stroke or functional outcome. AUTHORS’ CONCLUSIONS: Since the last version of this review none of the three new relevant studies with 2397 participants have provided additional information to change the conclusions. Treatment with a low-molecular-weight heparin or heparinoid after acute ischaemic stroke appears to decrease the occurrence of deep vein thrombosis compared with standard unfractionated heparin, but there are too few data to provide reliable information on their effects on other important outcomes, including death and intracranial haemorrhage.