The accuracy of the underwater and airborne horizontal localization of different acoustic signals by the northern fur seal was investigated by the method of instrumental conditioned reflexes with food reinforcement. For pure-tone pulsed signals in the frequency range of 0.5-25 kHz the minimum angles of sound localization at 75% of correct responses corresponded to sound transducer azimuth of 6.5-7.5 degrees +/- 0.1-0.4 degrees underwater (at impulse duration of 3-90 ms) and of 3.5-5.5 degrees +/- 0.05-0.5 degrees in air (at impulse duration of 3-160 ms). The source of pulsed noise signals (of 3-ms duration) was localized with the accuracy of 3.0 degrees +/- 0.2 degrees underwater. The source of continuous (of 1-s duration) narrow band (10% of c.fr.) noise signals was localized in air with the accuracy of 2-5 degrees +/- 0.02-0.4 degrees and of continuous broad band (1-20 kHz) noise, with the accuracy of 4.5 degrees +/- 0.2 degrees.