A single-lever shock avoidance conditioning technique was used to generate auditory behavioral thresholds for Lemur catta over the frequency range 100 Hz to 75 kHz. The results indicate a sensitivity of at least 60 dB below one dyne/cm2 from 1 kHz to 32 kHz and, throughout the entire frequency range, appear to be compatible with other available prosimian data. A contrast between anthropoids and prosimians indicates a loss in high frequency sensitivity for the former group, but a greater sensitivity for lower frequency stimuli. Analysis of lemur vocalizations indicates a preponderance of relatively low frequency components. Descriptions of the conditioning technique, threshold criteria, and procedures of sound measurement are included.