Aim. To study the role of eosinophil granulocytes in the development of restenosis after drug-eluting stent (DES) implantation. Materials and methods. The blood levels of eosinophils, eosinophil cationic protein (ECP), immunoglobulin E (IgE), and C-reactive protein (CRP) were compared in 170 patients with coronary heart disease (CHD) and stable angina who had undergone recoronarography within the first year after endovascular myocardial revascularization using DES. The blood level of eosinophils was determined by the results obtained employing the FACS Calibur flow cytofluorometer (Becton Dickinson, USA). That of ECP, IgE, and CRP was estimated by enzyme immunoassay by means of an Immulite-100 analyzer (Siemens, Germany). The data were presented as median (25th percentile and 75th percentile). Results. The blood eosinophil level was 272 (234; 292) cells/µl in patients with restenosis while that was 134 (85; 156) cells/µl in those without restenosis (p=0.002). The plasma ECP level proved to be greater in the patients who had developed restenosis after DES implantation than in those who had not [17.7 (11.2; 24) and 9 (6.4; 12.9) ng/ml, respectively (p=0.017). At 6 months after DES implantation, the level of ECP was significantly higher (8.6 (7.3; 9.7) ng/ml) than the baseline level (p=0.04). Later on, there was an even greater increase in ECP levels. No significant changes were noted in blood ECP levels after bare stent implantation. Conclusion. The findings suggest that there is a relationship between the occurrence of restenosis and the enhanced activity of eosinophil granulocytes in CHD patents after DES implantation.