Objective: Coronary slow flow phenomenon has been arbitrarily defined as delayed coronary blood flow in the absence of obstructive coronaryartery disease. The present study sought to investigate the clinical features, natural history, and outcomes of affected patients. Methods: In this prospective cross-sectional study, 217 consecutive patients who had undergone coronary angiography and showed featuresof coronary slow flow phenomenon were evaluated for demographic and coronary risk factor profile, as well as clinical outcomes, at baselineand following treatment. Results: The study population consisted of 165 (76%) males and 52 (24%) females. The mean age of patients was 52.6±10 years. Mean ejectionfraction was 48.2±5.4, 39.3% had diabetes, 43.3% had hypertension, 49.8% was a cigarette smoker, 41.9% had dyslipidemia, and 15% had afamilial history of cardiac disease. Forty-nine percent was detected to have abnormal hsCRP levels. The most prevalent presenting complaintwas atypical chest pain. Fifty-four percent of patients had slow blood flow in all three vessels. Thirty-six people had undergone repeat coronaryangiography in a follow-up period of 5-7 years due to persisting or worsening clinical symptoms, of whom 6 (16.6%) showed significant coronaryartery stenosis. Eight (22.2%) had mild CAD, and the rest still showed coronary slow flow without significant stenosis. The most common com- plaint during follow-up and after initiation of medical therapy was nonanginal chest pain. Conclusion: Patients with coronary slow flow phenomenon are predisposed to atherosclerosis and obstructive coronary artery disease.Therefore, this pathology should not be considered as a totally benign condition. Primary and secondary cardiovasculature preventive mea- sures should be constituted and seem worthwhile in this patient population.