Hemodynamic properties of both bioprostheses and mechanical valves have improved over the years, however, direct comparison between second-generation porcine and bileaflet valves is rare. Therefore, by the mean of Doppler echocardiography, we determined hemodynamic performances in 45 patients with Medtronic Intact bioprostheses in the aortic position and in 67 patients with bileaflet mechanical valves. Differences in pressure gradients between the two groups were essentially attributable to differences in annulus size. Indeed when the transvalvular gradient was stratified according to annulus size, mean values were no longer significantly different between Medtronic Intact porcine valves and bileaflet mechanical valves for each annulus size. In conclusion, Medtronic Intact bioprostheses in the aortic position exhibit similar hemodynamic characteristics compared to bileaflet mechanical valves.