Recent advances in microsurgery and myocutaneous flaps have induced many surgerns to consider skin flaps from a new point, and this has produced an interest in the fundamentals governing flaps. If the flap is longer and larger, it should be delayed for complete survival,but delay requeires considerable time . Therefore, as a substitute for delay, vascular anastomosis in the distal part of a flap will theoretically give the same effect. In this study, we investigated the importance of arterial inflow in the distal side of a flap in a rat. The experiment was done in 3 groups according to design of flaps and in each group, 3 subgroups was made. In A flap, the superficial epigastric artery was preserved or anastomosis. In B flap, both superficial epigastric artery and vein was preserved or anastomosis. In C flap, both artery and vein was severed. In result, C flap in all 3 groups were completely survived. In conclusion, we suggest the possibility that a large flap may be transposed in oen stage with vascular anastomosis in the distal part - preferably artery and vein, or artery only.