Introduction: This study was performed to investigate the effect of vitrification procedure using ethyleneglycol as cryoprotectant on the follicular morphology of neonatal ovarian tissue of mouse after thawing andautotransplantation. Material and Methods: Ovaries from 3 weeks neonate NMRI mice were excised then vitrified in asolution of DMEM medium containing ficol 70, sucrose, acetanied and ethylene glycol (EGFS 40%) andstored in liquid nitrogen. After thawing with 1 M sucrose solution and equilibration with DMEM medium, some vitrified-warmed andfresh ovarian tissues were studied morphologically and the others were autografted intraperitoneally. Fourweeks after transplantation, animals were sacrificed and the fresh and grafted samples were fixed and studiedunder light microscopy. Results: Our results showed that there was no statistically significant difference between the normalfollicles in vitrified, toxicity tested and fresh control ovaries. After transplantation statistically significant differences was observed between normal follicles in intactcontrol, transplanted-control and vitrified-transplanted groups (P<0.014) and these rates were 98.18% ,89.33% and 91.54% respectively. In the transplanted group the number of follicles had a relative decrease andthe ovarian tissue was invaded by fibrous and fat tissue. However follicles in different developmental stageswere located in the periphery of ovarian tissue. Conclusion: Our observations showed that this procedure is useful and efficient for preservation ofneonatal mouse ovarian tissues and can be used for preserving the reproductive potential of infertile patientsin the future. However it is necessary to improve maturation conditions such as changing the site oftransplantation.