Dynamic stress intensity factors (DSIFs) are important fracture parameters in understanding and predicting dynamic behavior of a cracked body. To evaluate DSIFs for both homogeneous and nonhomogeneous materials, the interaction integral (conservation integral) originally proposed to evaluate SIFs for a static homogeneous medium is extended to incorporate dynamic eÞects and material nonhomogeneity, and is implemented in conjunction with the finite element method. In this study, a research code is developed and verified using benchmark problems. Then, various homogeneous and nonhomogeneous cracked bodies under dynamic loading are employed to investigate dynamic fracture behavior such as the variation of DSIFs for different material profiles, the relation between initiation time and the domain size (for integral evaluation), and the contribution of each distinct term in the interaction integral.