The present studies, the investigations were undertaken for an attemp to analyze time course change of biogemic amines in respons to bite injury in rats and guinea pigs, and obtained the following results that might be applicable to the forensic medicine and Forensic Odontology. The histamine concentrations measured at rat abdominal skins were decreased during the first 8 hours and recovered to control levels after 12 hours. However the serotonin concentrations were decreased during the first hours and increased during 4-8 hours, and then returned to control levels thereafter. In contrast with these results, both histamine and serotonin concentrations were tended to increase in guinea pig skins, but the concetration of histamine showed maximum rate of increase immediately after injury and those of sertonin showed maximum rate of increase at 30 minutes. The differencd in the response of histamine and serotonine after injury between rats and ginea pigs revealed that there is specials deffrence in the response of biogenic amines with regard to external stimuli. These results suggest that the determinition of biogenic amines in skin lesion of bite marks could be applied to the estimation of the elapsed time after antemortem injury.