Abstract: Fresh skin of guinea pigs was treated with 10% dimethylsulfoxide and 1: 5000 furacin in Kreb’s Ringer phosphate for 15 minutes. The treated skin was divided into three groups. Skin of group one was immersed directly into liquid nitrogen, that of group two was pre-cooled with dry ice for 4 hours, and that of group three was pre-cooled in a slow cooling apparatus, the cooling rate of which being adjusted to 1℃ per minute. After-79℃ was reached, the skin was transferred to a dry ice container. The total pre-cooling time was also 4 hours. Skin of group 2 and 3 were then immersed in liquid nitrogen. Forty-eight hours later, all specimens of skin were thawed in 40℃ water bath, and they were examined under electronmicroscope. The ultrastractures of the rapidly cooled skin showed significant changes. The nuclei of the basement layer appeared irregular in arrangement, chromatin abnormally aggregated, mitochondria vacuolized and cristae disappeared. The microfilaments of cytoplasm were arranged in irregular manner. In some epidermal cells, there were a large number of wacuoles or large fissures in cytoplasm. There was lysis of nuclei in various degrees. Intercellular spaces disappeared. The cells which were closer to the cornified layer were more severely damaged. The main characteristic features of the skin pre-cooled in dry ice were irregularities of nuclei and spotty lysis of chromatin. There were also large fissures in cytoplasm. Some cells were "swollen". It was our impression that skin which was cooled down gradually appeared less altered. In the basement layer, the cells appeared almost normal, except for an enlargement of intercellular space and twisted nuclei. But in the thinner skin, lysis of nuclei, vacuolization of cytoplasm, irregularity of microfilaments in various degrees may sometimes be found in the basement and prickle cell layers.