Five patients with oropharyngeal cancer treated with 5-fluorouracil and cisplatin had ischemic stroke within 2 to 5 days after the drug infusion. This occurred during the second course of chemotherapy in three patients, and during the third course in two patients. There may be a relation between treatment and brain infarction because 1) there was no other cause identified despite extensive tests, including postmortem examination in one patient; 2) there was a short delay between treatment infusion and stroke; and 3) there was a similar pattern of ischemic stroke after the second or third course of chemotherapy.