Aim. Toassessof the effect of cryopreservation by vitrification on morphofunctionalparametersof immature rat testicular tissue in a cryoprotective media based on polymeric carriers. Methods. Samples of immature rat testicles were rapidly immersed in liquid nitrogen under protection of the cryomedium 1 (15 % DMSO+18 % glycerol+0.5M sucrose) or the cryomedium 2 (15 % DMSO+18 % glycerol+15 % PEO) based on biopolymers (bovine serum albumin (BSA), collagen (CG) or fibrin (FG) gels). The comparison groupsincluded theintact control and fragments vitrified in Hank’s solution. Results. In contrast to BSA and CG, FG had a more pronounced protective effect. Its combination with the cryomedium 1 led to a decrease in the degree of retraction and desquamation of spermatogenic epithelium, as well as to a three-fold increase incell density compared to the negative control. The metabolic activity of testis tissue vitrified under protection of FG and the criomedium 1 increased 2.75 times compared tothe negative control (BSA and CG inthis cryomedium led to 2.1- and 2.0-fold increase, respectively). A similar trendwas observed in the LDH activity. Biopolymers in thecryomedium 2 had a positive effect uponhistological examination, but did not contribute to the preservation of metabolic activity of spermatogenic epithelial cells. Conclusion. Cryomedium 1 based on fibrin gel had the optimal properties among all studied combinations of biopolymers and cryoprotectants. The obtained data can be used for development of vitrification methods for human seminiferous tubules.