The effect of impact velocity and displacement on pulmonary injury in rabbits was investigated by producing a series of nonpenetrating anteroposterior sternal impacts involving velocities of 5 to 18 m/s and displacements of 2 to 45 mm. Contusion of the bronchial region was dominant at impact velocities below 6 m/s and displacements above 20 mm;​ contusion of the alveolar region was dominant at impact velocities above 15 m/s and displacements above 2 mm. When impact velocity and displacement were high, both bronchial and alveolar regions were injured. Pulmonary injury severity, expressed as a severity index adopted from the Abbreviated Injury Scale 1976 (AIS), correlated well with impact displacement at a given velocity but poorly with the peak reactive force, impulse transfer, peak esophageal pressure, or the amount of available energy.