BACKGROUND: Absorption of autologous fat graft in the recipient area necessitates recurrent fat transplantation. Harvesting extra tissue during the first operation and storing it for future use is considered a solution to this problem. METHODS: Fat tissue was removed from the inguinal region of 40 Swiss albino mice, which were arranged into four equal groups, and treated as follows: immediately transplanted to the donor animal; dry-frozen; immersed in glycerol; or frozen in liquid nitrogen. The grafts that were frozen or immersed in glycerol were stored at -35°C for 6 months and then transplanted to their original donors. Transplantations were performed by injecting the fat under the scalp. Viability of the fat tissue was evaluated with the MTT reduction test before transplantation, and histology of the transplanted tissue was examined at the end of the study. RESULTS: The viability and histology of grafts frozen in liquid nitrogen were similar to those of fresh tissue, whereas with other methods the grafts had a considerable loss of viability during storage that was reflected in the low number of adipocytes and high proportion of vacuolar and fibrotic areas. CONCLUSION: Freezing fat grafts in liquid nitrogen and storing them at -35°C is an effective way of preserving tissue for future use, with clear superiority over other methods. ©2006 American Society of Plastic Surgeons.