Doppler velocimetry with the use of transesophageal echocardiography can record flow in the proximal left anterior descending artery (LAD). To assess whether this limited sampling ability influences the recording of velocity and the calculation of coronary flow reserve (CFR), 32 patients with LAD stenosis (4 ostial stenoses, 18 proximal stenoses, 10 mid-LAD stenoses) and 33 patients with arteriographically normal LADs were studied. Basal flow and dipyridamole-induced hyperemic flow rates were recorded. The mean basal flow velocity in ostial stenoses was greater than in other groups, and the mean basal flow velocity in proximal stenoses was less than that in mid-LAD stenoses and in the normal group. Maximal hyperemic velocity did not differ between the groups. CFR in all stenoses groups was less than that in the normal group. Ostial CFR was less than in all other groups, and proximal CFR was less than that in either the mid-LAD or the normal LAD groups. With this technique, coronary flow velocimetry and estimation of CFR is affected by the location of stenosis.