Background: Patients with AMI show varying degrees of collaterals. Various soluble factors are thought to be involved in recruiting collateral circulation. However, the relationships between various angiogenic factors and presence of collaterals are not well known. Methods: We evaluated 59 patients (age, 59짹10 years) with STEMI undergoing primary PCI. Patients were divided into group I (Rentrop collateral grade 0 or 1, n=34) or group II (grade 2 or 3, n=25). Blood samples were collected prior to PCI and 24h and 48h after PCI to determine plasma levels of VEGF, soluble VEGF receptor (sVEGFR), angiopoietin (Ang)-2, and soluble Tie-2 by ELISA. Results: Baseline characteristics were similar between the two groups. However, there were less diabetic patients and higher incidence of previous angina in group II. Plasma levels of Ang-2, Tie-2, sVEGFR were most elevated initially prior to primary PCI and gradually decreased after PCI, whereas VEGF rose after PCI and reached its maximal value at 48h. Plasma levels of VEGF, sVEGFR, and Tie-2 showed no difference between the two groups at any timepoint. However, Ang-2 was higher in group I compared to group II before as well as after primary PCI Conclusions: Early formation of collateral circulation in AMI patients was associated with lesser rise and faster fall in plasma level of Ang-2. VEGF showed delayed response to acute ischemia compared to Ang-2. Rise of Ang-2 in patients with AMI seems to be a compensatory reaction to acute myocardial ischemia. However, The detailed interaction and role of various angiogenic factors needs to be investigated in further studies.