Background : Lipoprotein(a) [Lp(a)] has been known to inhibit fibrinolysis system and promote thrombus formation in vitro, it may prevent spontaneous reperfusion in patients with acute myocardial infarction. In this study, we investigated the influence of Lp(a) on the infarct artery patency in acute myocardial infarction. Method : In 101 consecutive patients with acute myocardial infarction (male 81, 41.2 years old), coronary angiogram was performed within 10 hours of the onset of symptoms and antegrade flow in the infarct related artery (IRA) was scored according to the TIMI criteria. Lp(a), lipid profile and CRP was measured before coronary angiography examination. Result : The IRA was LAD in 44 (43.5 %), LCX 17 (16.8 %) and RCA 40 (39.6 %). The level of Lp(a) in TIMI 0 group showed significantly higher than in TIMI 3 group, but there were no significant differences among other groups (Figure). There were no differences in lesion site of IRA or number of diseased vessel. The duration from the onset of pain to angiography was similar. The CRP level and incidences of other risk factors such as diabetes mellitus, hypertension, hyperlidemia, obesity, and smoking showed no differences according to the TIMI grade. Conclusion : Higher level of Lp(a) inhibits the infarct artery patency in acute stage of myocardial infarction. This result suggests that Lp(a) may inhibit endogenous thrombolysis in human and affect the prognosis of acute myocardial infarction.