This study investigated the characteristics of the phasic flow velocity pattern of the right coronary artery and the relationship to hemodynamic parameters in patients with aortic stenosis. Coronary flow velocities were recorded at the proximal (segment 1) and the distal (segment 4PD) portion of the right coronary artery using a Doppler guide wire (0.014-in, 15 MHz) in 10 patients with aortic stenosis and 8 control subjects with normal coronary arteries. The diastolic to systolic peak velocity ratio at both the proximal and distal portion were significantly greater in patients with aortic stenosis than in control subjects. Systolic flow reversal was not seen in the right coronary artery in control subjects, but it was observed in 5 patients (50%) at the proximal portion and in 10 patients (100%) at the distal portion. Peak velocity of flow reversal at the distal portion showed a significant correlation with mean pressure gradient across the aortic valve (y = -1.3x + 37.3, r = 0.71, p = 0.02). Systolic flow reversal is characteristic in the right coronary artery, especially at the distal portion, in patients with aortic stenosis. This may be related to the pressure difference across the aortic valve through the posterior descending artery.