A ray‐tracing program which has been developed for the IBM 704 and 7090 computers yields results which show excellent agreement with experimental data. The program permits ray computations for arbitrary source and receiver depths, bottom profiles, and velocity structures. The tabulated results give actual ray trajectories as well as the geometrical spreading associated with each path. Realistic curves of transmission loss as a function of range can be determined by adding individual ray intensities, once reflection loss values have been introduced. Theoretical results were compared with a 100‐cps transmission loss curve obtained using a CW projector and a bottomed hydrophone in a deep ocean area of the North Atlantic. Good agreement was observed at moderate to long ranges. Significant errors at short ranges were attributable in part to the lack of refinement of the methods used. (This work was supported by the Bureau of Ships, U. S. Navy Department.)