To evaluate the feasibility and usefulness of transthoracic Doppler echocardiography (TTDE) as a non-invasive method in recording distal anterior descending (LAD) coronary flow velocity, we compared coronary flow reserve (CFR)measured by TTDE with measurements by intracoronary Doppler wire (ICDW). Twenty-one patients without LAD stenosis were studied. ICDW performed at baseline and after intracoronary injection of 18 µg adenosine. TTDE was performed at baseline and after intravenous adenosine (140 µg/kgmin for 2 min). Adequate Doppler recordings of coronary flow velocities during systole were obtained in 14 of 21 study patients (67%) and during diastole in 17(81%) patients. Baseline and hyperemic peak diastolic flow velocities measured by TTDE were significantly smaller than those obtained by ICDW (p<0.05). However,diminishing trends of diastolic and systolic velocity ratio after hyperemia were similarly observed in both methods. CFR obtained by TTDE (3.0±0.5), was higher than the value calculated by ICDW (2.5±0.4). There were significant correlations between the values obtained by the two methods (r=0.72, p<0.01). It is concluded that TTDE is a feasible method in measuring coronary flow velocity and appears to be a promising non-invasive method in evaluating CFR.