Color flow imaging (CFI) allows real time visualization of intracardiac and transvalvular blood flow, superimposed on two-dimensional echocardiographic images. Therefore it can be useful in the identification and characterization of spatial configuration of jets through valve prosthesis. The aim of this study was to define the transvalvular flow pattern of jet in 54 patients (pts) with mitral valve prosthesis which were functioning well. Thirty-six of these pts were females and 18 males; their ages ranged from 40 to 73 years, mean age: 58. Prosthetic mitral inflow was evaluated utilizing the parasternal long axis, apical long axis and apical 4 chamber views; in addition ("off axis") intermediate sections were used when needed. Adequate CFI for detailed frame by frame analysis was obtained in 50 pts (92%). Fourteen pts had biological prosthesis (9 Hancock, 4 Carpentier-Edwards, 1 Ionescu-Shiley). Thirty-six pts had mechanical prosthesis: 13 Björk-Shiley, 8 Starr-Edwards, 9 Sorin, 5 Lillehey-Kaster, 1 Smeloff-Cutter. Variable jet configurations were identified, which were related to the type of prosthetic valve. Bioprosthetic valve characteristically had a wide, homogeneous transvalvular flow, directed towards the interventricular septum. Björk-Shiley prosthesis presented typically a jet with two components. Trans-prosthetic flow was dependent on the spatial position of the prosthesis and on the orientation of the tilting disc. Thus, the main jet, coming from the major orifice, could be directed towards the apex, flowing parallel to the left ventricular postero-lateral wall while the jet coming from the minor orifice was thin and directed towards the interventricular septum.(ABSTRACT TRUNCATED AT 250 WORDS)