The measurement of cardiac output by the Doppler-echocardiography method is of considerable interest since, in contrast to other available techniques, it offers the possibility of the measurement of output at each valve orifice, thus providing a quantitative approach to valve regurgitation. The 4 basic data items required are: the surface area of the valve orifice, trans-valvular Doppler velocity spectrum, duration of ejection and of filling, and heart rate. A large number of studies have analysed the various investigation techniques and have shown their excellent correlation with reference invasive methods. In the light of experience acquired in our Echocardiography Laboratory, we recommend, in accordance with data from the literature, the exclusive use of pulsed Doppler and measurement of valve orifices by two-dimensional imaging at the point of insertion of the aortic and sigmoid cusps as well as at the mitral ring. A simplified method for the measurement of mitral surface area on the basis of TM records is suggested.