Résumé : A multicentre, double-blind, randomized study was performed in 179 patients with acute ischaemic stroke resulting in limb paresis. The purpose was to compare the safety and efficacy of Org 10172 (1250 anti-Xa Units s.c. once daily) and heparin sodium (5000 IU s.c. twice daily) in preventing deep-vein thrombosis (DVT).Prophylaxis started within 72 hours of the onset of stroke and continued for at least 9 days. To detect DVT, patients underwent a daily 125I fibrinogen leg scanning which, if found positive, was followed by venography. A first computed tomography scan of the brain was performed at screening to rule out cerebral haemorrhagic and second at cessation of treatment to detect any haemorrhagic transformations. At the 2-3-months' follow-up period the patients were examined for signs and symptoms of DVT or pulmonary embolism.On an intention-to-treat analysis, DVT occurred in 14.6% of patients receiving Org 10172 and in 19.8% of those receiving heparin during the treatment period (p=0.392, NS). Pulmonary embolism was diagnosed in one patient in each group. Major conversion to a symptomatic haemorrhagic brain infarct was found in one patient in each group. Death occurred in 13.5% of patients treated with Org 10172 and in 6.7% of patients treated with heparin (p=0.135, NS). Deaths were mainly related to pulmonary infection and cerebral oedema, thus considered to be due directly to the clinical status of the patients.1250 anti-Xa Units of Org 10172 once daily is both safe and as effective as 5000 IU of heparin sodium twice daily given for DVT prophylaxis in patients with acute ischaemic stroke of recent onset. © 1994 British Geriatrics Society.