A new stentless pericardial prosthesis was designed for better hemodynamic performance and reduction of stress load compared with current stented bioprostheses. Between September 1997 and August 1998, the Quadrileaflet mitral valve (QMV) was implanted in 17 patients (mean age 62.2 ± 16.3 years; preoperative NYHA class 3.06 ± 0.2; ejection fraction 64.1 ± 14.7%). Echocardiography was performed pre-, intra- and postoperatively, and at 3-6, 12 and 24 months follow up. Implanted prostheses were small (n = 4), medium (n = 8) or large (n = 5). Mean cardiopulmonary bypass time was 138.3 ± 37.0 min; mean cross-clamp time was 91.3 ± 26.3 min. Postoperatively, the mean valve orifice area was 2.5 ± 0.4 cm², transvalvular velocity (Vmax) 1.6 ± 0.4 m/s, and mean pressure gradient 3.6 ± 2.0 mmHg. Echocardiography at 3, 6 and 12 months showed no significant difference from intraoperative data. At 12 months the mean NYHA class was 0.6 ± 0.7. The QMV is a promising alternative to conventional biological mitral valve replacement, though further follow up is needed to confirm these favorable mid-term results.