Background : Experimental studies support an important role for endothelial nitric oxide synthetase (eNOS) in the regulation of angiogenesis. We hypothesized that decreased NO bioavailability may limit collateral development in patients with coronary total occlusion. Objectives: This study aimed to evaluate the relation between the plasma level of nitric oxide metabolites (nitrite and nitrate) as an indicator of NO bioavailability and coronary collateral development in patients with chronic total coronary artery occlusion. Methods: 42 patients with chronic total coronary occlusion were grouped according to presence or absence of good collaterals to G1 and G2 and 20 healthy controls (G3). Collateral assessment was done in the patients using the collateral flow grade and the recipient filling grade. plasma nitrite and nitrate were also measured. Results: Good collaterals were found in 45.2% while poor collaterals were found in 54.8% (p = 0.001). By multivariate analysis, 4 variables were independently associated with poor coronary collateral: female gender, smoking, diabetes mellitus and low plasma NO metabolites (p = 0.036, 0.001, 0.001, 0.04 and 0.002) respectively. After adjusting for the different predictors the low plasma nitrite and nitrate were powerful predictors of poor coronary collateral development (p = 0.03 and 0.02) respectively. Conclusion: Our finding suggesting a beneficial role of NO bioavailability in coronary collateral development may highlight the role of NO bioavailability-improving agents as a promising therapeutic target in patients with an advanced coronary atherosclerosis.