A cerebral contusion and DAI (diffuse axonal injury) are very important in a medicolegal cases of the closed head injury. In this paper, I will report the epitome of the recent advances in the study on the biomechanics of them. Coup contusion can be mainly attributed to the skull inbending and/or the skull fracture. As to the mechanism of the contrecoup contusion, several theories are reported. They are Holbourn's rotation theory, Gurdjian's theory (anatomical features of the skull), Gross's cavitation theory, Lindenberg's theory (deformation force and acceleration one) and Courville's theory (transmitted of waves of force). As to DAI, Gennarelli's theory (high rate of angular acceleration operating for a long period). As to the brain injuries including a cerebral contusion and DAI, Ommaya's centripetal theory and Willinger's theory (natural frequency of impact) are reported.