This prospective study was conducted to compare hemodynamic parameters measured by the Doppler echocardiography of ON–X heart valve with TTK Chitra mechanical valve in the mitral area. The study was conducted on 100 patients operated only for mitral valve replacement. At the time of discharge and in follow–up visits detailed 2 –D Echo with Colour Doppler examination was done focusing on trans–valvular mean gradient, mitral valve area by Pressure Half Time (PHT) and Continuity Index. Both the groups of prosthesis provided a satisfactory hemodynamic and clinical outcome in early postoperative period for valve sizes greater or equal to 25 mm. From our study result we conclude that the haemodynamic data were not significantly different between the two groups. Both TTK Chitra and ON–X mechanical valves provided a satisfactory hemodynamic and clinical outcome in early postoperative period for valve sizes greater or equal to 25 mm. ON–X valve was easier to insert and gave more favourable post–operative hemodynamic performance with lesser gradients and larger effective orifice area. ON–X valve are technically easier to implant especially when total preservation of sub–valvular apparatus is done