The present work describes the development and testo f a whole-field velocimetry system for measuring transient velocity fields in extensive flow regions. The technique employed is known as Particle Image Velocimetry. In this technique, double-exposure images of tracer particles distributed in the fluid and externally illuminated are registered in film or electronic camera. The images are digitized and processed by specially developed computer algorithms based on cross-correlation and autocorrelation techniques. The computer program developed was tested against computer generated flow images. A experimental setup was constructed to capture and analyze several real flow images. The tests conducted with several low-velocity flows yielded satisfactory results.