It is assumed that tissues with different degree of imminological privileges have a number of distinctions in the processes of reparation. This may be associated with mast cells, which are found in all body tissues of an organism, secrete a wide range of biologically active substances and are important in the regulation of repair processes. This paper present the results of investigations of morphometric parameners and functional activity of mast cells in tissues with varying degrees of immune privilege (skin, testis). It has been shown that migration of must cells in the skin is observed early after the injury and followed by a slow increase of synthetic activity and index of degranulation of mastocytes within 30 days. Index of degranulation of mast cells in the testes increased immediately after the injury in the absence of their pronounced migration. Stabilizing membranes of mast cells using the drug ketotifen led to inhibition of the repair of the skin, which was manifested itself in the absence of increasing the thickness of dermis, epidermis, the number of fibroblasts and collagen fibers, and also in slowing down the formation of scar. At the same time, the inactivation of mast cells promoted reparative regeneration of testes as was indicated by increase in the number of normal spermatogonia which are proliferative pool for all subsequent stages of spermatogenesis, and by considerable decrease in the number of non-functioning tubules. Thus, the number and the functional sate of the mast cells have an impact on the course of reparative processes in tissues with varying degrees of immune privileges.