During the last few years the use of the noninvasive doppler-echocardiography method to study left ventricular relaxation and filling has aroused considerable interest owing to its excellent feasibility. However, it is now known that the filling flow rate may vary according to several parameters including filling conditions, heart rate, patient's age, site of measurement and medication, so that the curves obtained must be interpreted with extreme caution. Apart from this, doppler-echocardiography is invaluable not only to distinguish between physiological and pathological left ventricular hypertrophy, but also to detect heart transplant rejection.