Mean horizontal velocities of sound propagation in the ocean, defined as the ratio of the horizontal range to the one‐way travel time, have been measured. Single‐dimension RAYDIST equipment is used to measure the horizontal distance between source and receiver, and a radio link is used to determine the one‐way travel time. Measured mean horizontal velocities are compared with values computed by ray‐tracing methods for which the sound‐velocity profile is obtained fromin situbathythermograms. Comparisons of mean horizontal velocities are presented out to ranges of 15 miles for combinations of source and receiver in and below the surface duct.