Histopathologic and ultrastructural changes in the tissues of frozen extremities of Wistar rats were investigated immediately after thawing. Three experimental groups were formed: two were exposed to cryoinjuries of different intensity, while the third was the control one. Cryoinjury was caused by experimental model of local, controlled freezing of hind, right extremities. Immediately after thawing the tissue samples were taken from frozen right and unfrozen left extremities, in which histopathologic and ultrastructural changes were compared mutually and with control group, respectively. It was observed that the freezing directly caused ultrastructural and histopathologic damage of the tissues that were manifested immediately after thawing and were proportional to the intensity of freezing. Simultaneously, in the tissues existed complex circulatory disorders manifested in open arteriovenous shunts, venous congestion and microcirculatory insufficiency caused by evident spasm of arteriolae that could be considered to be very significant pathogenetic factor in ischemic damage of unfreezed tissues.