The relationship was investigated between the postmortem intervals and the rectal temperatures of 35 persons who had died at known times and had been subjected to medico-legal autopsies after exposed to changed environments. The influence of air temperature, body size and cause of death upon the cooling rate of cadaver has been found to be complex and not to be analyzed quantitatively. It has been concluded that the time of death cannot be estimated merely by means of the temperature reading of cadaver.