The basic auditory functions and the perception of vowel-like vocal sounds (grunts) were studied in the chimpanzee. The chimpanzee showed a W-shaped auditory sensitivity function. The chimpanzee was more sensitive to 1-kHz and 8-kHz than 2-kHz and 4-kHz tones. It was found that the first formant was more important than the second formant for the perception of these vocal sounds. The chimpanzee did not vocalize vowel-like sounds [i] and [el. The relationship between the perception of grunts and the auditory sensitivity function and between the perception and the production of grunts of the chimpanzee was discussed.