This study surveyed the vocalization repertoire of descendants of wild-trapped Rattus rattus. Sound recordings synchronized with behavioral observations were conducted in an animal colony living undisturbed under seminatural conditions. Analyses of sound recordings revealed 10 distinct acoustic signals, 5 of which were in the ultrasonic frequency range. The time course and the frequency pattern of the analyzed sounds were similar to those described for R. norvegicus, and they occurred in comparable situations. A species-specific difference may be the intensity of the emitted sounds. The possible communicative function of the acoustic signals is discussed.