Aim: Coronary artery disease (CAD) and its serious clinical form, ST segment elevated myocardial infarction (STEMI) has been the leader within the death causes around the world and in our country. In STEMI, the main objective is providing the myocardial reperfusion. In our study, it was aimed to investigate the predictive value of tenascin-C level for the degree of myocardial reperfusion in patients with STEMI. Methods: In our study, 58 patients admitted to our hospital with acute anterior STEMI were included. All the patients had underwent primary percutaneous intervention for the single-vessel disease at left anterior descending coronary artery. After admission to coronary care unit tenascin-C levels were measured. Subjects were classified according to their myocardial blush grades (MBG); MBG 0, MBG 1 and MBG 2 were groupped as Group I, MBG 3 was groupped as Group II. The groups were compared according to their tenascin-C levels and other parameters. Results: Between group I (n = 31, mean age 55 +/- 12.5) and group II (n = 27, mean ages 49.3 +/- 11.1); tenascin-C, troponin I and CK-MB levels were significantly higher in group I compared to the group-II (P < 0.001; P < 0.001 and P < 0.05; respectively). In group I, left ventricular ejection fraction (LVEF) was significantly lower (P < 0.001), left ventricular end-diastolic volume and left ventricular end-systolic volume were significantly higher (P = 0.03) as compared to group II. In group I, ST-segment resolution at ECG was worse (P = 0.003). In correlation analyzes, tenascin-C was significantly positively correlated with troponin-I (r = 0.596; P < 0.001) and CRP (r = 0.615, P < 0.001). Tenascin-C was significantly negatively correlated with MBG, LVEF and ST-segment resolution (r = -0.626, P < 0.001, r = -0.411, P = 0.002 and r = -0.631; P < 0.001, respectively). Conclusion: Based on our study, it can be estimated that in patients with high tenascin-C levels myocardial reperfusion was inadequate, even underwent successfull PCI. In this context, increased tenascin-C may help predict not only left ventricular remodelling and prognosis but also the effectiveness of primary PCI.