Doppler is an essential tool for the echocardiographer. Color, pulse wave, and continuous wave Doppler allow for the visualization and measurement of blood flow through the heart, allowing assessment for valvular abnormalities, noninvasive measurement of pulmonary arterial pressure, diastolic functioning, and stroke volume. This chapter discusses techniques for optimizing the use of Doppler tools and provides an overview of individual clinical applications of Doppler during a focused echocardiography.