Full thickness skin wounds in hooded Lister rats of the Rowett Institute strain kept at an environmental temperature of 30° C closed more rapidly than did those in similarly wounded rats housed at 20° C. The differences were statistically significant. This response was exhibited by both sexes and was found in experiments carried out at both Aberdeen and Glasgow.The wounds in male rats were found to close more rapidly than those in female rats housed at the same temperature. The rectal temperature of the animals was not affected by the environmental temperature but the temperature of wounded skin was significantly higher (ca. 0.9° C) in the animals held at 30° C. Also in these latter rats, the response of skin temperature at the wound margin differed markedly from those at 20° C.Rats at 20° C pair fed to rats at 30° C, who even prior to wounding eat less than those at 20° C, did not respond differently from rats allowed food ad libitum at the lower temperature.The epithelium of the wounds advanced at a linear rate in the final stages of closure.