In order to establish a guide line for the timing of early and safe division of skin flap pedicle by measuring the transcutaneous oxygen pressure(TcPO₂), daily transcutaneous oxygen pressure level and the flap survival were compared in pedicle skin flaps developed on the back of rabbits. Results were as follows ; 1) The transcutaneous oxygen pressure ratio of flap to normal control was lowest in the 1st day group of rabbits, and increased significantly in the 3rd, 4th, 5th day groups of rabbits. The transcutaneous oxygen pressure of flap reached that of normal control in the 5th day group. 2) As for flap survival, total necrosis was observed in the 1st, 2nd, 3rd day group, partial necrosis was observed in the 4th day group. Full survival was observed in the 5th day group. 3) TcPO₂ measurement in the flap may be a useful guide in determining the timing of pedicle devision in skin flaps.