Background: TRAIL is a member of the tumor necrosis factor(TNF) family of cytokines which plays important role in regulating cell death and inflammation. It is well known that the TRAIL kills tumor cells selectively by inducing apoptosis. However the biologic activity of TRAIL on vascular endothelial cell is uncertain. Methods: We enrolled 81 consecutive patients(mean age: 49짹11yrs, M:F=60:21) underwent coronary angiogram and spasm test with intracoronary acetylcholine(Ach) injection. The plasma TRAIL levels were determined in blood samples obtained at the time of coronary angiogram. We classified the subjects as normal control(NC, N=28(35%)), equivocal vasoconstriction(EVC, N=20(25%)) and significant vasospasm(SVS, N=33(41%)) according to the severity of coronary vasoconstriction in coronary spasm test(NC���30%, 30%< EVD���90%, SVC>90%). Results: 1.The median TRAIL level of all subjects was 13.3pg/ml ranging from 2.1 to 35.9 pg/ml. 2.The TRAIL levels were not associated with age, body mass index(BMI) and gender difference. 3. The TRAIL levels were not related with the presence or absence of diabetes mellitus(DM), hypertension, smoking history and hyperlipidemia. 4. The TRAIL levels of SVS group were significantly decreased compared with those of NC (median(interquartile range), 10.3(3.7) vs 15.3(7.5)pg/ml, p<0.01) and SVS(10.3(3.7) vs 14.8(6.2)pg/ml, p<0.05). 5. After adjusting age, sex, DM, hypertension, and smoking history, the plasma TRAIL level was independently associated with SVS(p<0.05, 95% confidence interval:0.841-0.988). Conclusion: The plasma TRAIL level was negatively correlated with coronary vasoconstriction after intracoronary Ach injection. It might suggest that TRAIL might exert a protective role on vascular endothelial cell survival.