The impact responses of the fracture parameters of interfacial crack tip, such as energy release rate (J integral), stress intensity factors (K), crack opening displacement (COD) and T stress, under the dynamic loading condition were studied using both numerical and experimental methods. A three point bending impact test was performed with bimaterial specimens composed of aluminum and polymethyl methacrylate (PMMA). Fracture parameters for the interfacial crack tip were calculated by a programmed post processor which used both the domain integral method and the interaction energy method. The interaction energy method showed good performance in the decomposition of stress intensity factor and the calculation of elastodynamic T stress with path independency. The phase angle of stress intensity factor varied with time. The relationship between energy release rate and phase angle at the onset of crack propagation showed unsymmetrical U shaped curve. COD showed same result with the result of stress intensity factors. The magnitude of the T stress was not enough to affect the plastic deformation. Specimens whose T stress were less than zero exhibited stable crack growth along the interface as expected in the analysis. (C) 2001 Published by Elsevier Science Ltd.