Background: Gamma-glutamyl transferase (GGT) levelwas found to be elevated in plasma of patients with cardiovascular risk factors. The aim of our study was to assess the relationship between serum GGT levels and the occurrence of no-reflow as well as to evaluate the prognostic value of GGT in ST-segment elevation myocardial infarction (STEMI) population. Methods and Results: One hundred sixty-eight consecutive patients with STEMI who underwent percutaneous coronary intervention (PCI) were enrolled in the study. Patients with STEMI were grouped into tertiles according to their admission serum GGT levels. No-reflow after PCI was assessed both angiographically (thrombolysis in myocardial infarction [TIMI] flow and myocardial blush grade) and electrocardiographically (ST resolution). Gamma-glutamyl transferase levels were higher in patients with STEMI compared to the elective PCI group subjects. Patients with angiographically (TIMI flow ≤2 or TIMI flow 3 with final myocardial bush grade ≤2 after PCI) and electrocardiographically (ST resolution <30%) detected no-reflow were increased in number across the GGT tertiles. In addition, 1-year mortality rates showed a significant increase across the tertile groups (4% vs 11% vs 23%, P < 0.01). Multivariable logistic regression analysis revealed that GGT levels on admission were a significant predictor of long-term mortality of myocardial blush grade-detected no-reflow phenomenon. High GGT level on admission was a significant predictor for long-term mortality and major adverse cardiac events. Conclusions: In patients with STEMI undergoing primary PCI, high GGT levels at admission were found to be associated with no-reflow phenomenon and increased long-term mortality. Copyright © 2012 American Federation for Medical Research.