The aim of this study was to assess the validity of mitral valve blood flow measured by pulsed Doppler echocardiography (PDE) with the sample volume positioned at the tips of the mitral leaflets. Thirty patients with a mean age of 38.4 years underwent calculation of transmitral blood flow: by Touche's method (A) in which the mitral orifice is assumed to be an ellipse with a constant long axis equal to the diameter of the mitral annulus and a variable short axis equal to the distance between the mitral leaflets measured on the M mode recording. The velocities are recorded by PDE with the sample volume at the tips of the mitral leaflets. The instantaneous cardiac output is equal to the surface multiplied by the instantaneous velocity. The integration of the instantaneous outputs throughout the whole of diastole by a computer programme provides the stroke volume; by a simplification of this method (B) which considers the short axis of the mitral ellipse to be constant and equal to the mean mitral valve leaflet separation measured from the M mode recording, and; by Hoit's method (C) which calculates mitral valve surface area from the M mode recording alone. The transmitral blood flow was calculated by these three methods and compared to the classical PDE aortic cardiac output measurement during the same examination, the accuracy of which has been previously demonstrated.(ABSTRACT TRUNCATED AT 250 WORDS)