The audibility function of the squirrel monkey was measured with particular interest in determining the high-frequency cutoff. The animals were trained to lick a tube to produce a tone burst. This response served to fix the animal's head in the sound field. A barpress within 3 sec of tone onset produced food and was counted as a detection. The squirrel monkey audibility function obtained had a low-frequency slope of approximately 10 dB/octave, the typical notch at 4 kHz and maximum sensitivity in the 8–10-kHz region. The high-frequency side was complex, consisting of a decrease of sensitivity to 16 kHz, a flat portion from 16 to 32 kHz, and a sharp cutoff commencing between 32 and 40 kHz. The 70-dB-SPL point occurred at 46 kHz.