This study was to estimate the Doppler haemodynamic profiles of 56 prosthetic mitral valves (St Jude prosthesis) in the premature post-operating period, to study the correlation of the prosthetic area calculated by Doppler method (continuity equation (CE) and pressure half times (PHT)) and the area of the effective orifice in the post-operating premature period, in 6 weeks and after 6 months. The values of peak gradient and mean gradient at six week and at 12.5 months were not significantly different from those obtained in the premature exam. The prosthetic area calculated by continuity equation (ACE) in the premature postoperative period was significantly different between the various size (p = 0.0001). The (ACE) measured at 6 weeks and late (12.5 months), was not significantly different from that calculated in the premature exam (respectively p = 0.79 and p = 0.8). The (PHT) was very variable even within the different size of the prosthesis, however values measured at six weeks and in the late exam was not different from that calculated in the premature exam. In absence of complications, it seems to us that we can satisfy with using as reference exam data obtained in the premature exam.