Dural sinus thrombosis developed in two children with acute lymphoblastic leukemia during induction treatment with vincristine sulfate, prednisone, and asparaginase. Headache, nausea, emesis, and lethargy were the presenting signs. The diagnosis was confirmed by arteriography. The cause is presumed to be secondary to hypercoagulability due to asparaginase-induced antithrombin III deficiency. The patients received anticoagulation therapy and recovered completely. Only two of the six reported patients without heparinization survived.