Antithrombotic drugs (especially heparin and aspirin) are widely used to treat patients during the acute phase of ischemic stroke, yet there is no evidence of any beneficial effect on the course of the disease. Although these drugs can reduce the risk of such complications as deep venous thrombosis and, possibly, the number of recurrences of stroke, they can also give rise to systemic or cerebral hemorrhage. Given the uncertainty about the efficacy and safety of antithrombotic drugs, and specifically about the risk/benefit ratio, large clinical trials are needed to determine the indications for their use in the management of acute ischemic stroke. We stress the importance, because of its magnitude, of the International Stroke Trial (IST), the results of which will be available in 1996.