Results of two studies concerning the interrelationship of velocity, compression and injury in blunt thoracic impact to anesthetized swine have been combined to provide a data base of forty-one experiments. impact velocity ranged from ∼8-30 m/s and applied normalized chest compression from ∼0.10-0.30. Experimental subjects were suspended in the spine-horizontal position and loaded midsternally through a 150 mm diameter, flat rigid disk on an impacting mass propelled upward from below. Measurements and computations included sternal and spinal accelerations, intracardiovascular overpressures, physiological responses, injury, as assessed by necropsy, and different forms of the velocity and compression exposure severity parameters.The significance of both compression and velocity as parameters of impact exposure severity is clearly demonstrated. Qualitatively, exacerbation of injury was seen when either variable was increased with the other held constant. Quantitatively, better logistic regression models were found relating the probability of heart rupture and of AIS ≧ 4 to products of velocity and compression, including the viscous response, than to normalized compression or peak spinal acceleration alone. Dynamic overrun of the ventral thorax and gross cardiac damage involving multiple focal rupture lesions were uniquely associated with the 30 m/s exposures.