BACKGROUND: Thrombomodulin concentration greatly increases in plasma when vascular endothelial cells are injured, and it is one of the specific molecular markers for endothelial injury.OBJECTIVE: To analyze the plasma levels of thrombomodulin after cerebral infarction or hypertension, and to compare levels with those from healthy control subjects.DESIGN: A case-controlled observation. SETTING: Yuquan Hospital of Tsinghua University.PARTICIPANTS: Patients with hypertension (n = 37) and acute cerebral infarction (n = 26) were selected from the outpatient and inpatient Department of Neurology, Yuquan Hospital of Tsinghua University from February 2003 to February 2006. The cerebral infarction group consisted of 24 males and 2 females, 36–77 years of age, with a mean age of 62 years. All patients fulfilled the diagnosis criteria for cerebral infarction, according to the diagnostic standards revised by the Second National Academic Meeting for Cerebrovascular Disease, and were confirmed by CT or MRI. The hypertension group consisted of 27 males and 10 females, 36–77 years of age, with a mean age of 56 years. These patients fulfilled the diagnostic criteria for hypertension set by WHO. In addition, 43 healthy physical examinees were selected as the control group, consisting of 23 males and 20 females, 35–67 years of age.Informed consent was obtained from all participants.METHODS: In the cerebral infarction group, thrombomodulin plasma levels were determined by enzyme-linked immunoabsorbent assay at days 1, 3, 7, and 14 after attack. Thrombomodulin plasma levels were determined only once in the hypertension group and the control group. The results from the cerebral infarction group were compared with those from the hypertension group and the control group. MAIN OUTCOME MEASURES: Level of thrombomodulin in plasma.RESULTS: All 63 patients and 43 healthy volunteers were included in the final analysis of results. ① At 7 days after the attack, the plasma levels of thrombomodulin in the cerebral infarction and the hypertension groups were significantly higher than in the control group (P < 0.01). ② The plasma level of thrombomodulin was detected at four time points after cerebral infarction. It reached peak values on day 7, and it was lowest on day 14. CONCLUSION: The changes of thrombomodulin plasma levels could be used to monitor the severity of vascular endothelial cell injury in acute cerebral infarction.