Background. Stent thrombosis is potentially lethal complication with huge economic burden. The role of insufficient response to antiplatelet therapy is still unclear reason for its occurrence. Case report. We presented 54-year-old man with recurrent stent thrombosis on the 4th, 9th and 12th day after the primary percutaneous coronary intervention in spite of double antiaggregation therapy (aspirin+ clopidogrel). All possible procedural causes were excluded and reimplantation of intracoronary stent was insufficient to resolve the problem, so four platelet tests were performed: flow cytometry, Platelet Function Analyzer-100 test, aggregometry, and determination of gene polymorphism for P2Y12 receptor (directly involved in the mechanism of thienopyridine), and GPIIbIIIa receptor (final receptor in aggregation). The patient was the carrier of the major haplotype H1H1 for P2Y12 receptor and minor A1A2 for GPIIbIIIa receptor. The results of all the performed tests showed insufficient antiplatelet effect of aspirin and sufficient response to thienopyridin (not to clopidogrel, but to ticlopidine). Conclusion. Performance of platelet function tests is necessary in the case of major adverse cardiac events especially stent thrombosis, after implantation of intracoronary stent.