Power Doppler is a new method of ultrasound flow imaging the utility of which is currently under investigation. This technique creates a flow map based on the integrated power of the Doppler spectrum, rather than mean Doppler frequency. Power Doppler imaging is inherently more sensitive in terms of flow detection than standard color Doppler imaging; therefore, power Doppler can display flow for situations in which color Doppler is ineffective and can even display tissue perfusion in highly vascular organs such as the kidneys. Furthermore, power Doppler is not effected by aliasing, nor is it effected by blooming in the same way as color Doppler, which has deleterious effects on color Doppler flow images. The control of blooming with power Doppler may be of great importance in the clinical application of echo-enhancing agents. This review article discusses in detail the technological advantages and disadvantages of power Doppler flow imaging. In addition, it provides a synopsis of the preliminary research studies that have been conducted to date with respect to the clinical applications of power Doppler.