In order to understand the directional sensitivity of an echolocating system, directionalities of both emitted sounds and ears should be measured. The skull of Myotis grisescens was rigidly held with a nail cemented to it. FM sounds nearly identical to the species-specific orientation sounds were elicited by electric stimuli applied to the midbrain. The fields of 55-, 75-, and 95-kHz components in the FM sounds were measured with microphones moved around the bat's head. The amplitudes of these components were half at 30°–40° lateral, 25°–50° down, and 5°–20° up from the eye-nostril line. As expected, the higher the frequency, the narrower was the sound field. Directionality of the auditory system in terms of lateral lemniscal evoked potential was also measured at 55, 75, and 95 kHz. From these measurements, the directional sensitivity of the echolocating system was obtained, which was sharper for higher frequencies, but the most sensitive direction moved toward the midline with an increase in frequency, so that the most important cue for echolocalization, the interaural intensity difference, became smaller for higher frequencies.