Background: Slow coronary flow (SCF) is an angiographic finding characterized with delayed opacification of epicardial coronary arteries without obstructive coronary disease. Urotensin II (UII) is an important vascular peptide, which has an important role in hypertension, coronary artery disease, and vascular remodeling in addition to potent vasoconstrictor effect. Objectives: We investigated UII levels, hypertension, and other atherosclerotic risk factors in patients with SCF, a variety of coronary artery disease. Methods: We enrolled 14 patients with SCF and 29 subjects with normal coronary arteries without SCF. We compared the UII levels and the atherosclerotic risk factors between patients with SCF and control subjects with normal coronary flow. Results: UII concentrations were significantly higher in patients with SCF compared to controls (711.0 +/- 19.4 vs. 701.5 +/- 27.2 ng/mL, p = 0.006). We detected a positive correlation between SCF and age (r = 0.476, p = 0.001), BMI (r = 0.404, p = .002), UII concentrations (r = 0.422, p = 0.006), and hypertension (r = 0.594, p = 0.001). Conclusion: We identified increased UII levels in patients with SCF. We think that UII concentrations may be informative on SCF pathogenesis due to relationship with inflammation, atherosclerosis, and vascular remodeling.