In order to establish the polarizing microscopical characteristics of collagen in preserved dura mater transplants and in controls, a study was performed. Attempt was made for an intrpretation of velocity of collagen rehydratation by means of data of total anisotropy. The results show a faster rehydratation of collagen fibrils in control (unpreserved) dura mater. Changes in the velocity of rehydratation of collagen fibrils in lyophilized dura mater were connected with structural changes during lyophilization. The most appropriate period of time for rehydratation of lyophilized dura mater transplant was determined from the results of the polarizing microscopical study.