The temps. within the legs of living rabbits were observed when the legs were subjected to standardized conditions of exposure to cold. Subsequent clinical and anatomical changes were noted. Legs were subjected to temps. of +5[degree] to -40% for 30 min. Temps. were measured by means of thermocouples placed on the surface and at various points within the muscle. Autopsies were performed on the 7th or 8th day after exposure. In the range of +5[degree] to -5[degree] only temporary functional changes were noted. Exposure at -10[degree] and below produced tissue necrosis with a steep increase occurring between -12[degree] (33% necrosis) and -15[degree] (70% necrosis). Atrophy was an intermediate type of injury, usually beginning at -10[degree] to 12[degree]. Necrosis appeared first in the muscle and later in the skin. Tissue temps. were below freezing when the bath temp. was -5[degree] or less.