The vertical coherence of underwater sound in a convergence zone has been investigated by means of a vertical receiving array of six hydrophones spaced212 ftapart and hung at a depth of 3800 ft from a surface ship. A second ship towed a 1120‐Hz CW source outward in range from 28 to 43 miles. The outputs of the different hydrophones, when correlated together, yield correlation coefficients equal to nearly unity when in the convergence half‐zones at 30 and 38 miles, and show only a slow falloff with increasing separation. In between zones, where bottom‐reflected paths occur, the correlation coefficient was much smaller and was found to fall off faster with increasing separation. It may therefore be concluded that a vertical array located in the convergence zone of a distant source will experience a higher signal‐to‐noise ratio as a result of two effects: an increased signal level due to convergence, amounting to 10 dB in one experiment, and an increased array gain due to the greater coherence of the received sound.