A rapidly scanning directionally-sensitive three-velocity - component laser Doppler anemometer has been developed. It permits scans through 3-dimensional flows to obtain space-time velocity information. Since it has lower signal-averaging bias than pointwise measurements, only short record times are required to obtain sufficient data for statistical averages and, hence, it enables rapid mapping of the U, V, and W velocities in such flows. A flexible optical system allows for easy variation of the fringe spacings as well as the location and the size of the measurement volume. The optical paths are equalized without use of any additional optical components. A Ronchi Ruling is employed to create a horizontal stationary fringe pattern, and a dual Bragg cell is used to produce sets of moving vertical fringes. It is also shown that a scheme proposed by other workers, relying on a fringe pattern moving in the on-axis direction, will not work. The Doppler frequency is independent of the position of the receiving optics, and only one photomultiplier tube is needed to receive the signals for all three velocity components. Measurements made on a stationary solid object as well as in a dispersion of particles in water show that signals with low noise level and high fringe visibility are obtained. / M.S.