To investigate the characteristics of the phasic flow velocity pattern and its positional change in the right coronary artery (RCA), we studied 27 patients who had no significant stenosis in the RCA, and 8 patients with pulmonary hypertension (PH). Systolic and diastolic peak velocities (SPV and DPV), and systolic and diastolic time velocity integrals (SI and DI) in the RCA were measured by a Doppler guide wire at the proximal, mid, distal portions of the RCA, as well as at the RV branches. The diastolic to systolic peak velocity ration (DPV/SPV), and diastolic fraction (DI/DI+SI) were also calculated as indexes of the phasic flow velocity pattern. Results; At the proximal portion of the RCA, SPV equalled DPV. SPV and SI showed significant inhibition at the distal portion of the RCA, although DPV and DI showed no significant change. DPV/SPV and DI/DI+SI in the proximal portion of the RCA were smaller than those in the distal portion of the RCA and in the LCA. In the severe PH group we observed an attenuation of the systolic flow even in the proximal portion of the RCA and in the RV branches. Conclusion; The phasic flow velocity pattern changes as the position changes in the RCA.