In recent years, the universally used internal expansion by implanting a silicone elastomer balloon into the soft tissue under the skin has shown certain disadvantages, i.e., certain complications associated with the operation, high cost, and the fact that the materials cannot be recycled. That the materials are used only once adds to the operating cost. In view of these disadvantages, we have designed and developed a kind of mechanical external skin expander, which is composed of (1) an adjustable tractor, (2) preserving splints, and (3) a traction frame. The tractor is used to grip the contracted skin in order to make the soft tissue of the skin expand with the lapse of time and increase in traction weight. The external skin expansion has the following advantages compared with internal expansion: avoiding the complications caused by implanting the soft-tissue expander beneath the skin; simplicity and efficiency of operation; and the fact that the equipment can be reused, reducing the operating which is suitable for these basic units. The data of the expanded skin area can be calculated through the computer. Since June of 1993, a satisfactory curative effect has been obtained in 44 patients suffering from advanced postburn scars. Thirty-two patients among them were treated for more than half a year, with the scar becoming normal in both appearance and function. External skin expansion provides a new method for expansion of skin soft tissue. It has a bright future in its clinical application.