The injection of autologous free fat obtained by suction-assisted lipectomy for the correction of soft tissue defects is a common procedure in plastic surgery. However, unpredictable partial absorption of the injected fat often necessitates repeated harvesting and injection. Fat preservation for future re-injection is indicated to avoid repeated fat harvesting procedures. A previous study has shown that fat obtained by suction can be preserved by freezing for at least 2 weeks. The purpose of the present study was to investigate the effect of freezing autologous free fat for 7 months on the take of the fat graft. Human fat obtained by suction-assisted lipectomy was centrifuged and stored in a domestic refrigerator at -18 degrees C for 7 months. After thawing, the fat was injected into the scalp of 10 nude mice, which served as the study group. In the control group (n = 10), fresh fat was injected. Fifteen weeks later, the fat grafts were dissected out. Volumes, weights, and histological parameters were compared between the groups. The injected fat survived in both the study and the control groups but the histological parameters were significantly inferior in the frozen fat. The weight of the frozen fat was also significantly less compared with the fresh fat. The volume of the frozen fat was inferior but not significantly. Based on this in vivo experiment, it is suggested to refrain from using fat that has been frozen for 7 months or longer. The longest period and the optimal conditions for fat preservation should be further investigated.