The well‐known SOFAR channel manifests itself in modified form for sound sources situated off axis. Sources are usually closer to the ocean surface than to the axis, and in such cases high‐intensity “convergence zones” may appear at spacings of some 20 to 35 mi depending on latitude and on velocity conditions. Formed usually by deep “refracted‐surface reflected” rays the caustic structure of a zone is known. These convergence zones are analogous to the zones of sound which alternate with zones of silence in abnormal sound propagation through the atmosphere. Recent publications giving the ray theory and specific details of the uw sound propagation have created a situation in which both much and little information is available. So that this situation may be relieved, a review of both experimental and theoretical efforts will be attempted. These efforts were carried out by both government and contracting laboratories. Accomplishments in recent years have shown that convergence zone propagation is common and predictable. Methods of fairly precise intensity computation exist but entail considerable effort. The existing computations, theory and experiments provide enough information so that convergence‐zone propagation in the first several hundred mile range interval can be adequately described. Merging and confusion of zones is to be expected at greater ranges.