Over the past six decades, echocardiography has evolved into an important technique for not only imaging cardiac structures, but also, by employing the Doppler equation, for assessing cardiac blood flow and tissue velocities. This review focuses on pulsed Doppler echocardiography: its principles, early development, and clinical applications. Important clinical applications include: (1) measurement of flow velocities, stroke volumes, and regurgitant and shunt volumes; (2) assessment of time intervals, e.g., pulmonary artery acceleration time as a measure of pulmonary artery pressure and resistance or the timing of mitral regurgitation in hypertrophic cardiomyopathy; (3) detection of turbulent flow in regurgitation, stenoses, and shunts, enhanced by the implementation of color Doppler; and (4) evaluation of left ventricular diastolic function in conjunction with pulsed tissue Doppler and deformation (strain) measurements.