Objective:　To　evaluate　the　endocrine　function　and　lymphocyte　infiltration　of　ultrarapidly　frozen　newborn　rat　ovaries　in　adult　recipients.　Design:　Animal　study.　Setting:　Reproductive　Medicine　Laboratory　of　Ningxia　Medical　College.　Animal(S):　Newborn　rats　within　24　hours　after　birth　and　Sprague-Dawley　female　adult　rats.　Intervention(S):　Newborn　or　adult　rat　ovary　tissues　were　cryopreserved　with　ultrarapid　freezing　method,　using　1.5　M　propylene　glycol　and　0.1　M　sucrose　as　a　cryoprotectant　agent.　After　thawing,　they　were　allotransplanted　under　the　kidney　capsule　of　ovariectomized　adult　female　rats　to　assess　the　function　and　the　microstructure.　Main　Outcome　Measure(s):　Vaginal　smear,　serum　E2　level　in　recipients,　grafts　histologic　observation,　3　beta-hydroxy　steroid　dehydrogenase　histochemistry　staining,　and　CD4(+)/CD8(+)　T　cell　immunohistochemistry　staining.　Result(S):　Frozen-thawed　newborn　rat　ovaries　survived　and　established　a　vascular　network　with　the　kidney　of　recipients.　More　growing　follicles　were　found　in　these　survival　grafts.　No　significant　differences　were　found　in　both　resumption　rates,　the　day　of　initiating　estrous　cycles,　and　E2　level　between　the　frozen　adult　and　frozen　newborn　rat　ovaries　transplant　group.　Among　all　the　groups,　the　number　of　lymphocyte　in　the　frozen　newborn　rat　ovary　transplant　group　is　the　lowest.　Conclusion(s):　This　is　the　first　report　for　ultrarapid　cryopreservation　that　can　preserve　the　development　potential　of　immature　ovaries　in　ovariectomized　adult　recipients　and　further　reduce　their　immunogenicity　successfully.