Doppler mitral flow velocities and related variables are used to assess left (LV) and right ventricular filling and, indirectly, ventricular diastolic function. Three abnormal ventricular filling patterns (impaired relaxation and pseudonormal and restrictive physiology) are recognized in patients with various heart diseases and have been related to alterations in LV diastolic properties and filling pressures. More recently, these variables have been used to assess the hemodynamic effects of drug therapy or heart surgery and prognosis in patients with restrictive and dilated cardiomyopathies. Despite these encouraging results, widespread clinical use of these Doppler techniques has been hampered by difficulties in obtaining accurate and reproducible measurements from Doppler flow velocity recordings. This is due, in part, to an underappreciation of factors such as cardiac filling mechanics, Doppler examination principles, and ultrasound machine settings, which can markedly affect the quality of the flow velocity recordings. The purpose of this article is to provide the technical information for performing a systematic and comprehensive Doppler evaluation of LV diastolic function that can be used on a routine basis. This information includes discussing the different flow velocity recordings required for a Doppler assessment of LV diastolic function, their proper recording technique, and the common technical pitfalls.