Perimortem damage recorded on bone indicates the immediate processes affecting animals or humans at or near the time of death. In many cases the agents producing the modifications may be identified based on modern comparative studies. Perimortem alterations or injuries may occur as a result of human action, the subject of forensic studies, and it is clearly important to distinguish these from other taphonomic processes and agents. We describe those modifications occurring at the time of death, including linear marks, pits and perforations, rounding of ends of bones, cracking of bone tissues, digestion, discoloration and staining, breakage and fragmentation, and disarticulation, with added notes about later occurring modifications that mimic the perimortem modifications.