The skin extensibility was measured at 12 anatomical sites of the living body using the BIO-SKIN TENSION METER equipped with a strain-gauge. The subjects were 82 healthy males whose ages ranged from four months to 73 years. The differences in degree of extensibility according to age are summerized as follows. Two age groups, the below one year old and the one-to-two year-old group, showed significant extensibility in most, but not all of the measured sites. The 50-year-and-older group did not show any significant differences in the degree of extensibility as compared to the 20-29 year-old group. Degree of wound retraction, would closing tension and skin extensibility were measured after the first and second operations of serial excision. Results of measurements are summerized below. The highest degree of decreased extensibility was observed at 3 months after surgery, and the recovery of skin extensibility was observed at 6 to 9 months postoperatively depending on the measuring sites and excised widths. Serial excision yielded more satisfactory results than one stage excision with regard to suture of the wound due to the reduced degree of wound retraction and closing tension. An interval of 6 months between operations was recommended for serial excision on face of less than 20 mm, on arm of less than 30 mm and excision of less than 35 mm on the trunk, and an interval of 9 months was judged to be appropriate for serial excision exceeding 50 mm on trunk. Recommended excision widths in serial excision for children are as follows; less than 30 mm on the face, less than 45 to 50 mm on the arm, less than 85 to 100 mm on the trunk.