Objective: There have been numerous investigations demonstrating protective effects of awell- grown coronary collateral circulation (CCC) on left ventricular systolic function. N-terminal pro-B-type natriuretic peptide (NT-pro-BNP) is released by ventricular myocardium as a result of increased myocardial wall stress. The aim of the study was to evaluate the relationship between CCC and plasma NT-pro-BNP levels. Methods: Study group was retrospectively selected from patients who had a coronary angiography at our center between January 2008 and December 2009. One hundred and thirty patients having at least one totally occluded main coronary artery were included in this study. Collateral circulation was graded according to Rentrop score. Grade 0 and 1 are regarded as poor, and grade 2 and 3 - good CCC. Plasma NT-pro-BNP levels were measured by electrochemiluminescence immunoassay method and left ventricular ejection fraction (LVEF) were measured by modified Simpson method. We used Chi-square, Student t and Mann-Whitney-U tests for statistical analysis. Results: Overall 57 patients were found to have poor CCC and 73 patients have good CCC. Plasma NT-pro-BNP levels (pg/ml)-median (minimum-maximum)- were 1319 (48-9753) in poor CCC group and 847 (16-5529) in good CCC group (p=0.004). LVEF was found to be -median (minimum-maximum)- 45% (30-55%) in poor CCC group and 50% (30-60%) in good CCC group (p=0.003). Correlation analysis demonstrated that collateral grade was negatively correlated with NT-pro-BNP levels (r=-0.252, p=0.004). Conclusion: We found that plasma NT-pro-BNP levels were more elevated in patients with poor CCC than in patients with good CCC. This finding may be explained with the protective effect of good CCC on LVEF.