Lipoprotein(a) (Lp(a)) is a low-density lipoprotein (LDL)-like particle that may accelerate atherogenesis and promote thrombosis. In the present study, relationships between serum Lp(a) levels and the severity of coronary artery disease and infarct artery patency were studied in 14 patients with acute myocardial infarction. Lp(a) was measured by enzyme-linked immunosorbent assay and the timing of reperfusion was evaluated using the creatine kinase myosin-brain fraction and myoglobin release curves. Thrombolysis in Myocardial Infarction (TIMI) flow grade and severity of coronary artery disease were assessed using a scoring system based on coronary angiography performed during hospitalization and 6 months thereafter. The median Lp(a) level on admission was 127 (range 11-2,513) mg/l. The overall coronary score was higher in patients with Lp(a) levels greater than 127mg/l than in those with Lp(a) less than 127mg/l (P < 0.01). Lp(a) level correlated with the coronary score measured during hospitalization (r = 0.80, P < 0.01) and 6 months later (r = 0.79, P < 0.01). The timing of reperfusion and infarct artery patency were not depen dent on the serum Lp(a) level. The results show that the serum Lp(a) level is associated with the angiographic severity of coronary artery disease postmyocardial infarction bu does not determine the patency of the infarct-related artery.