The von Willebrand factor (vWF) levels increase in acute-phase ischemic stroke because of endothelial dysfunction and thrombus formation and may reduce acetylsalicylic acid (ASA) efficiency in hemostatic cascade. The aim of the study is to investigate the relationship between vWF levels and ASA resistance in ischemic stroke patients. Fifty acute ischemic stroke patients (mean age 66.3±13 years, 34 males) were given 300 mg/day aspirin for at least 10 days, and 25 healthy volunteers as a control group were compared using platelet function analyzer-100 test. All risk factors were investigated for a correlation to ASA resistance. ASA resistance was apparent in 32% of the study group and in 20% of the control group (p=0.140). vWF levels were elevated in only ASA nonresponders and the ischemic stroke group that showed a statistically significant association with aspirin resistance (p≤0.05). vWF levels increase in ASA nonresponders and ischemic stroke group in acute phase. High vWF levels may relate to ASA resistance and recurrent strokes.