1. Responses of single neurons in the torus semicircularis of leopard frogs (Rana pipiens) to changes in the horizontal position of sound were investigated. Three auditory stimuli consisting of tone bursts at the unit's best excitatory frequency (BEF), noise bursts and simulated mating calls were used for this study. 2. With a few exceptions, all torus neurons showed strong responses to changes in the sound direction (directional responses) with one or all three different acoustic stimuli. 3. Two differerent types of directional responses were noted: Type I response was characterized by approximately equal responsiveness to sound coming from either side of the animal whereas sound from the frontal field elicited poor responses; Type II response was characterized by sigmoidal response as a function of the azimuth, i.e., pronounced response to sound derived from the contralateral field and which became weaker as the source was moved around the animal to the ipsilateral field. The majority of directionally sensitive torus neurons exhibited type II responses. 4. The neural parameter that was systematically altered with a change in the incident angle of the source was either the average firing rate (class I), or response latency (class II) of the first spike, or both (class III). 5. In three specimens, one of the eighth nerves was sectioned and directional responses of torus neurons were studied and compared to those from the intact animals. It was found that the monaural responses were similar to those responses seen in intact animals but with smaller overall change in the response with a 180 ° change in the incident angle of the source demonstrating that binaural inhibitory interaction could sharpen the receptive field of central auditory neurons. 6. The results of the present investigations provide evidence suggesting that both the directionality of the peripheral receiver and central binaural processing are involved in sound localization.