The principal characteristics of the investigations into the mechanisms of gunshot injuries are considered. The general and peculiar features of gunshot fractures and the pathological processes underlying them are discussed. The theory of bullet impact effect put forward by the Russian surgeons in the late XIXth century is verified. The explanation is proposed for the physical nature of direct and side impacts and the phenomenon of a temporary oscillating cavity from the standpoint of the theory of bullet impact effect. The new forensic medical criteria for the gunshot origin of an injury have been developed that allow the gunshot distance and the geometric characteristics of the bullet to be determined. A methodological basis for the determination of the long-range gunshot distance has been created. The results of the present study may be of interest for criminal lawyers and military specialists.