The purpose of this study was to observe the revascularization after transplantion of, the skin flap. The free flap or pedicled flap has been used in the oral and maxillofacial surgery for the reconstruction of defects after a radical cancer surgery or an extensive trauma. The pedicled flap was more frequently used than the free flap because of its better. blood supply. Several methods, which can be used as an evaluating device for survival of the skin flap, have been performed in many researches. In recent years, the improvement in the technology of the high-molecular chemistry has made us possible use the acrylic resin injecting into the b11ood vessels of the living animals to evaluate the revascularization of the skin flap. In this study 12 rabbits weighing about 1.8 Kg were used. The right side ears were used as the control group and the left side ears were used as the experimental group. 12 animals were divided into 6 groups composing of 2 animals in each group. The flap operations for each group were performed at the same day. The each experimental group was sacrificed by the injection of the acrylic resin into the common carotid artery at the 1st, 3rd, 7th, 14th, 28th, and 42nd day after the operation. The ears of the both groups were digested by the concentrated Hcl for 48 hours and then the resin frameworks were washed under the tap water. Thereafter, the resin frameworks were dried at the room temperature, and observed under the stereoscope. The following results were obtained: 1. Capillary vessels in the flap withered on the 1st day after flap transplantation and increased in number on the 3rd day and with the increase of venules and arterioles, they were decreased on the 2nd weeks. 2. On the 3rd day, blood vessels in the flap were arranged to the longitudinal direction of flap. 3. At the proximal junction of flap and margin of recipient bed of denuded area, arterioles were severely undulated and strangulated. 4. Until 6th weeks, budding of neovascularization from the cutting end of blood vessels were unable to observe. 5. At the junction between the flap and recipient bed, venules branched from vein of flap and pre-existed arterioles are undulated and joined with the vessels of recipient bed at 2nd weeks. And undulation is not observed at 4th weeks and vascular system almost repaired to normal state.