['Erythropoietin (EPO) improves cardiac function and induces neovascularisation in post-myocardial infarction heart failure. The aim of this study was to analyse the association between the serum erythropoietin level and coronary collateral development in patients with coronary artery disease and chronic total occlusion.', 'A\xa0total of 168 patients consisting of 117 with coronary artery disease (CAD, (62 with chronic total occlusion (CTO), 55 without CTO)) and 51 with healthy coronary arteries were included in the study. The patients were assigned as coronary artery disease without CTO (group\xa00), CAD with CTO (group\xa01: poor collateral development, group\xa02: good collateral development) and normal coronary arteries (group\xa03).', 'There was a\xa0significant positive correlation between serum EPO levels and the Rentrop scores in angiography (r\xa0= 0.243, p\xa0= 0.001). Similarly, a\xa0positive correlation was found between serum EPO levels and the Syntax scores (r\xa0= 0.253, p\xa0= 0.001). Echocardiography revealed a\xa0negative correlation between serum EPO levels and the cardiac ejection fraction (r\xa0= -0.210, p\xa0= 0.006).'] Does erythropoietin stimulate the coronary collateral development in patients with coronary chronic total occlusion?