PURPOSE: The triad of chest pain, normal coronary arteries and a positive stress test has been called microvascular angina. The link between coronary flow reserve(CFR) and Duke treadmill score(DTS) in patients with microvascular angina remains elusive. METHODS: We studied 108 subjects (M:F=8:60, mean age 54+/-9 yrs) with chest pain and normal coronary angiogram. Exercise treadmill test(ETT) was performed by Bruces protocol and the equation for calculating DTS was DTS=xercise time- (5xST deviation)-(4x exercise angina), with 0=one, 1=onlimiting, 2=exercise-limiting. The coronary flow velocity at diastole(PDV) using Transesophageal echocardiography (TEE) was obtained from the proximal left anterior descending coronary artery and coronary flow reserve(CFR) was calculated as the ratio of hyperemic PDV after the intravenous infusion of dipyridamole(0.56 mg/kg) to baseline PDV. RESULTS: 1) CFR was 3.04+/-0.45 in group with negative ETT and 2.19+/-0.62 in group with positive ETT(p<0.001). 2) CFR was 1.51+/-0.31 in high-risk group with a score of <-10, 2.39+/-0.63 in moderate-risk group with scores from -10 to + and 3.04+/-0.43 in low-risk group with a score of > or =+ on DTS(p< 0.001 versus low-risk, respectively). 3) DTS was significantly related to CFR (r=.704, p<0.001). CONCLUSION: The composite DTS is closely related to CFR using TEE and might be a useful tool that can help clinicians determine the severity of ischemia and evaluate the efficacy of treatment in patients with microvascular angina.