Pathologically elevated body core temperature, measured at the death scene, is an important finding in medico-legal investigation of violent deaths. An abnormally high rectal temperature at any death scene may point to an underlying pathology, the influence of certain drugs or a hidden cerebral traumatism, and death by suffocation which would remain undetected without further medico-legal investigations. Furthermore, hyperthermia and fever, if unrecognized, may result in an erroneous forensic estimation of time since death in the early postmortem period by the “Henssge method.” By a retrospective study of 744 cases, the authors demonstrate that hyperthermia is a finding with an incidence of 10% of all cases of violent death. The main causes are: influence of drugs, malignant tumors, cerebral hypoxia as a result of suffocation, infections, and systemic inflammatory disorders. As a consequence it must be stated, that hyperthermia must be excluded in every medico-legal death scene investigation by a correct measurement of body core temperature and a comparison between the cooling rate of the body and the behavior of early postmortem changes, notably livor and rigor mortis.