There are many kinds of wide excision or wide resection, which are methods to remove the tumor with surrounding tissues. The curability of wide resection depends on the range and characteristics of the normal surrounding tissues. The fascia, periosteum and perivascular sheath act as barriers against invasion of tumors. Therefore, evaluation of the surgical margin is essential in surgery for malignancy. Some sarcomas characteristically show invasive growth patterns while others have a discrete border. Causes of the local recurrence are 1) insufficient surgical margin, 2) skip metastasis, 3) tumor thrombus, and 4) lymph node metastasis. The so-called "Safety surgical margin" is the margin that prevents local recurrence due to insufficient surgical treatment. Local recurrence due to other causes can not be treated by surgery alone as chemotherapy is also required. For example, the infiltrative type of malignant fibrous histiocytoma requires a curative procedure. On the other hand, non-infiltrative types of sarcoma or high-grade sarcoma, which are good responders to preoperative treatment, are locally controlled by an adequate wide margin procedure. When the tumor is close to the bone, main vessels and/or nerves, it is sometimes very difficult to preoperatively decide whether or not to sacrifice these important organs. A new surgical method, "In Situ Preparation (ISP)," is a useful method to solve such problems. ISP makes it possible to evaluate the surgical margin without contamination. And additional procedures including alcohol soaking or pasteurization can be achieved according to the surgical margin. Because ISP can prevent overtreatment, the number of our cases that require resection of the nerves or vessels have decreased. After a wide resection, there have been many possible complications, including infection, deep venous thrombosis, loosening of prosthesis, skin necrosis, and arterial occlusion. Once postoperative complications occur, patients must remain in the hospital for a long time. To prevent this, the preservation of normal tissue, meaning reduction of surgical margin, is important.