Histological and autoradiographic studies were performed to investigate the reparative processes during wound healing in kidneys after local freezing. 12h after freezing (-186°C, 30 sec) the cryonecrosis is fully developed. After the 5th postoperative day the cryonecrotic area shows a pronounced calcification of necrotic tubules. 30 days after freezing the reparation of the cryolesion in the kidney results in a small fibrous scar. The proliferative activity of the kidney parenchyma is limited to a small tissue area surrounding the cryonecrosis and reaches a maximum between the 2nd and 3rd postoperative day. 30 days after freezing there are no differences between the labelling indices after injection of 3H-thymidine one hour before killing the animals in frozen and in non frozen parts of the kidneys. These results are comparable to the findings in liver and spleen after deep freezing and underline the rapid repair of cryonecrosis in parenchymal organs especially in kidneys.