Objective: Although various inflammatory markers have been studied in patients with slow coronary flow (SCF), serum neopterin levels have not been studied previously. We investigated the serum neopterin and high sensitivity C-reactive protein (hs-CRP) levels and the relationship between neopterin and hs-CRP levels and TIMI flow in patients with SCF. Methods: The study group consisted of 51 patients with SCF. An age and gender matched control group was composed of 40 subjects. Coronary flow rates of all patients and control subjects were documented by Thrombolysis in Myocardial Infarction (TIMI) frame count. We measured serum neopterin and hs-CRP levels at the same time in patients with SCF and control subjects in this cross-sectional observational study. Chi-square, Mann-Whitney U and unpaired t tests, Pearson correlation and linear regression analyses were used for statistical analysis. Results: The TIMI frame counts for all coronary arteries and the mean TIMI frame count were significantly higher in the SCF group than controls. Serum neopterin levels were significantly higher among patients with SCF when compared with control group (2.13±1.03 vs. 1.60±0.50 ng/ml; p=0.004). Serum hs-CRP levels were significantly higher among patients with SCF when compared with control group (2.06±1.32 vs. 0.74±0.40 mg/L respectively; p<0.001). There was a significant association of serum neopterin levels (β=0.60, 95% CI: 4.93-9.06, p<0.001) and serum hs-CRP levels (β=0.29, 95%CI: 0.84-4.33, p=0.004) with mean TIMI frame count independent of potential confounders such as age, gender, body mass index, smoking, glucose and cholesterol levels. Conclusion: We have shown that serum neopterin and hs-CRP levels were significantly elevated in patients with SCF when compared with control subjects. Serum neopterin and hs-CRP levels were correlated with mean TIMI frame count in patients with SCF.