St. Jude medical hemodynamic plus series is positively used for aortic valve replacement (AVR) of small orifice because it can increase the orifice area by 26% compared with conventional prosthetic valves of the same size. We performed AVR with SJM 19A-HP on a patient having aortic stenosis with regurgitation using horizontal mattress suturing technique. The aortic orifice size was 18.9 mm at the preoperative measurement. The course after the operation was uneventful until 9 days after the operation when cinefluoroscopy revealed symmetrical restriction of opening of valve leaflets. We are now monitoring the clinical course at the patient has not developed any symptoms though the LV-Ao pressures gradient is 60 mmHg by Doppler echocardiography. As the restriction of valve leaflet opening was symmetrical, it is not likely that an excess of the ligature or remnant caused the restriction; structural problems of St. Jude medical prosthesis appear to be a more reasonable explanation. Since the orifice ring of this prosthesis is not reinforced, longitudinal forces applied to the hinge may alter the shape of the ring, thus restricting the movement of valve leaflets. In the present case, forced insertion of 19A-HP instead of more desirable 17-HP is considered to have caused longitudinal forces acting on the hinge.