Auditory units that responded to sound only when it originated from a limited area of space were found in the lateral and anterior portions of the midbrain auditory nucleus (nucleus mesencephalicus lateralis pars dorsalis, MLD) of the owl. The response properties of these units were studied in five barn owls (Tyto alba) using a remotely controlled, movable sound source under free‐field, anechoic conditions. The area of space to which such a unit responded was virtually independent of the nature (tone, click, or noise) and the intensity of the sound stimulus, and was defined as the unit'sreceptive field. Within a unit's receptive field could be found a small area to which the unit would respond with greatest vigor. This area of space was termed the unit'sbest area. Units in the lateral and anterior portions of MLD were systematically arranged according to the azimuth and elevation of their best areas. Units with contralateral best areas were located posterolaterally; units with ipsilateral best areas were located anteromedially. Elevation was arrayed along the dorsoventral axis with high best areas located dorsally and low best areas ventrally. [Work supported by NIH.]