Introduction: Glycoprotein IIb/IIIa (GP IIb/IIIa) is a platelet receptor composed of two subunits coded by individual genes. GP IIIa gene has two alleles: A1 and A2. The A2 allele determines higher platelet activity and was investigated many times as a potential risk factor of ACS. The influence of A1/A2 polymorphism on the prognosis in patients with ST-segment elevation myocardial infarction (STEMI) has not been analysed so far. Aim: Evaluation of the relationship between GP IIb/IIIa A1/A2 gene polymorphism and one-year prognosis in patients with STEMI treated with primary percutaneous coronary intervention (pPCI). Methods: 171 patients (23.9% – women, 39.7% – anterior MI) with STEMI treated successfully with pPCI as well as 121 healthy subjects from a reference group were enrolled in the study. Genotyping was performed using restriction fragment length polymorphism analysis (RFLP). In one-year follow-up the primary end point included deaths and infarctions. The following methods were used in statistical analysis: c2 as well as Mann-Whitney test, Kaplan-Meier survival analysis, Cox regression model and multivariate analysis. Results: The percentage of A2 allele carriers was similar in STEMI patients and in subjects from the reference group (27.4% vs. 21.5%, p=0.24). No statistically significant difference in the incidence of primary end point between the A1A1 homozygotes and A2 allele carriers (A1A2/A2A2 genotype) was observed among STEMI patients. In Cox regression analysis, the variables associated with death or MI were: ejection fraction (RR 0.912, p=0.01) and systolic blood pressure on admission (RR 0.97, p=0.049). The variables categorised as unfavourable predictors included: Killip class >2 and heart ratio on admission >100/min (p <0.05, log-rank test). Conclusion: No relationship between GP IIb/IIIa A1/A2 gene polymorphism and STEMI incidence as well as one-year prognosis in patients with STEMI treated with pPCI was documented.