Abstract Previous comparative studies of ultrasound-induced pulmonary hemorrhage in mice and rabbits suggested that sensitivity to damage was species dependent (O'Brien and Zachary 1994b). In order to understand better these differences in species more analogous to the human, 74 pigs and 75 rabbits were each exposed for 10 min at 1 of 6 acoustic pressure levels (0, 145, 290, 340 [rabbits only], 460 and 490 [pigs only] kPa) at an ultrasonic frequency of CW 30 kHz. Eighteen mice were used as positive controls (10-min duration at 145 kPa). Because pig lung has numerous physiological and anatomical similarities to human lung, it was selected as the appropriate animal model for these studies. Pig lung data were compared to rabbit lung data; rabbit lung data have already been compared with mouse lung data (O'Brien and Zachary 1994a). Comparative analyses and extrapolation of these experimental data are intended to provide a better scientific basis for understanding the potential biological effects of ultrasound on human lungs since such studies will probably never be conducted with humans. Under the same exposure conditions and lung assessment criteria, mouse lung was determined to be more sensitive to ultrasound-induced damage than that of the rabbit by a factor of 3.9, the rabbit lung was more sensitive to ultrasound-induced damage than that of the pig by a factor of 3.7, and the mouse lung was more sensitive to ultrasound-induced damage than that of the pig by a factor of 14.4.