We have analysed pure-tone audiometry curve of 361 Finnish conscripts who suffered acute acoustic trauma during their military service. In more than 75% of the ears the hearing loss was found in the high-frequency region (above 2 kHz). In the remaining 25% the speech frequency range was also affected. The main threshold shift started at 1 kHz in 8%, at 2 kHz in 49%, at 4 kHz in 19% and at 6 kHz in 6% of the ears. Impulse noise from large-calibre weapons and explosions appeared to cause low-tone hearing loss slightly more often than small arms fire. No etiological differences were apparent between the ears with dip-type hearing loss and ears with more abrupt-like hearing loss.