Objective: In this study, we sought to investigate the serum levels of high sensitivity C-reactive protein (Hs-CRP), N-terminal pro-brain natriuretic peptide (NT proBNP), erythrocyte sedimentation rate, leukocyte, thyroid hormone and fibrinogen levels in patients with coronary slow flow phenomenon (CSFP). Methods: A total of 82 patients with angiographically proven normal coronary arteries and slow coronary flow in all three coronary vessels (45 males and 37 females, mean age 59±11 years) and 34 patients with normal coronary arteries and normal coronary flow (19 males and 15 females, mean age 56±10 years) with similar risk profiles were included in this cross-sectional observational study. Coronary flow rates of all patients and control subjects were documented by Thrombolysis In Myocardial Infarction (TIMI) frame count, serum level of Hs-CRP, NT proBNP, sedimentation, leukocyte, free triiodothyronine (FT3), free thyroxine (FT4), thyroid stimulating hormone (TSH) and fibrinogen levels were measured. Statistical analysis was performed using t test for independent samples, Chi-square test and Pearson correlation analysis. Results: Hs-CRP (0.88±0.86 vs 0.36±0.35 mg/L, p<0.001) and NT proBNP (117.83±163.2 vs 47.33±30.6 ng/ml, p<0.01) were found to be significantly higher in patients with coronary slow flow compared with normal control group. There were no significant differences regarding thyroid hormones, fibrinogen, sedimentation rate and leukocyte count between two groups. The mean TIMI frame counts were positively correlated (r=0.454, p=0.001 and r=0.554, p=0.001, respectively) with plasma Hs-CRP levels and NT-proBNP levels. Conclusion: Hs-CRP and NT proBNP are significantly higher in patients with coronary slow flow compared with normal control group. Their increased levels are positively correlated with TIMI frame count.