The vocal repertoire of colonies of bullfrogs maintained in a seminatural environment in the laboratory consisted of a distinct set of stereotyped calls: (1) mating calls made only by males; (2) three types of calls involving territorial behavior—one type made only by males, one type made only by females, and a third type made by both males and females; (3) release calls made by both sexes; (4) warning calls made by both sexes; and (5) distress calls made by both sexes. Each call is characterized by a different gross temporal pattern. The periodicity of the temporal fine structure is different for each type of call, with the mating call having the highest periodicity (100/sec). The spectral distribution of energy in each call is concentrated in the range 200–2000 Hz. The bullfrog's auditory system is well suited to detect and encode the temporal and spectral features of the acoustic waveforms in these calls.