Twelve squirrel monkeys were exposed to pure‐tone stimuli at intensities and durations sufficient to produce, in six, repeated temporary threshold shifts (TTSs) from 15 to 25 dB and, in the remaining six, permanent threshold shifts (PTSs) from 10 to 20 dB. Thresholds were determined by means of an avoidance conditioning procedure similar to that of Clack and Herman (1963), in which observation intervals were signaled by the houselight and the animals required to press a bar if an auditory signal was presented, and to withold response if not. Following final behavioral testing, animals were sacrificed and the effect of the exposures upon hair cells was determined. This was accomplished with surface preparation techniques and phase microscopy. The organ of Corti was examined along its length and the number of missing and visibly damaged hair cells was determined for each of the inner and outer rows from a point 1 mm from the apex to a point 17 mm from the apex. There was no clear evidence of hair cell damage due to the exposure. It is concluded that pure‐tone stimulation sufficient to produce PTSs of 10–20 dB may not produce anatomical injuries to the organ of Corti that are detectable by phase microscopy.