Introduction: In this study, we sought to determine whether insulin resistance, which is investigated by homeostatic modelling, is related to slow coronary flow (SCF). Materials and Methods: A total of 24 patients with SCIF (4 females/20 males, mean age 47 +/- 12 years) and 32 patients with normal coronary artery (10 females/22 males, mean age 52 +/- 12 years) were included in the study. Baseline glucose, insulin and plasma lipid levels were measured. A standard oral glucose tolerance test (OGTT) was performed and post-challenge insulin levels were also measured. The index of insulin resistance was calculated with the homeostatic modelling [homeostatic model assessment for insulin resistance index (HOMA-IR)]. Results: There were no differences between the 2 groups with regard to age, lipid levels, blood pressure levels, history of smoking, fasting and post-challenge plasma glucose. Baseline insulin levels were augmented in the SCF group (9.64 +/- 5.93 vs 7.04 +/- 3.26, P = 0.041). HOMA-IR levels were not different between the study groups (2.20 +/- 1.44 vs 1.69 +/- 0.86, P= 0.129). Manifest insulin resistance was significantly higher in the CSF group as compared with the control group (25% vs 3%,P=0.01). Conclusion: Manifest insulin resistance is seen more frequently in patients with SCF.