Data on the threshold of audibility of underwater sound have been published, but virtually no data are available on the upper threshold of tolerance to underwater sound of high intensity. The present experiment was undertaken to obtain such data. Twenty‐three listeners, UDT (Underwater Demolition Team) and scientific personnel, were given audiometric tests preceding and immediately following exposure in a high‐intensity underwater sound field. The stimulus was a 1500‐cps tone of 1‐sec duration that was increased in 1‐db steps from 161 db (re0.0002 d/cm2) to 180 db. Masking from breathing noise of the open circuit SCUBA (Self Contained Underwater Breathing Apparatus) was eliminated by having the listener breathe during the 2‐sec interval between steps. The listeners indicated to the experimenter their “tolerance” limits by means of an electrical signaling device. Tests were run with and without foam neoprene hoods. The data indicate that the threshold of discomfort to underwater sound at 1500 cps is approximately 173 db for divers without hoods. A comparison is made with similar data for airborne sound. A shift in the visual field which occurred at the onset of the sound is discussed.