Skin defects could be repaired primarily by using skin stretching device developed by Hirshowitz. Primary closure with this instrument use viscoelastic property and creep of the skin characteristics, and it does not need the second operation and long time hospitalization. The skin stretching device is thus thought to be a simple and very useful method for the coverage of skin defect. Some clinical experiences and animal studies were reported previously, but in case of human being, some basic informations such as histologic change or safe guidelines were not suggested up to now. Nine cases of skin defects were closed primarily using this instrument from March 1996 to April 1998, and histologic change, oxygen saturation at the time of stretching, and skin extension pattern with clinical results were observed. Sizes of skin defects were varied from 4.5   1.8 cm to 20   11 cm and affected sites were 1 in face, 1 in upper extremity, 3 in abdomen and 4 in lower extremity. All defects were repaired primarily without significant complications such as skin necrosis or wound disruption. The resultant scars were not worse than other scars repaired primarily under the moderate tension. Extension rate was more prominent in wound margin than farther area. At the beginning of skin stretching, initial skin tension was 1.9 - 2.7kg(average 2.3kg) and oxygen saturation was changed into 42 - 78%(mean 64%) from 95% in normal wound margin. Fifty-one minutes were required from initial applicationat to reach the point of 1.5kg skin tension, and oxygen saturation was 70 - 86%(average 77%). In histologic evaluation, the thickness of epidermis and dermis was not changed meaningfully, but elastic and collagen fibers were parallel to extension direction and fragmentations of these fibers were shown more frequently.