Although gastric cancer is the common cancer in Asia, there is no prospective data on the incidence of VTE development during the postoperative period of gastric cancer surgery. In other words, Asian doctors including Korean clinicians don't know the exact incidence of surgery-related VTE. From their clinical experiences, most Korean surgeons think that the incidence of postoperative VTE development is rare. They also have much concern about the complications such as bleeding that might be caused by routine use of pharmacologic thromboprophylaxis during the perioperative periods. Therefore, in most clinical situation, Korean surgeons do not perform perioperative pharmacologic thromboprophylaxis using LMHW. Considering these clinical situations in Korea, the uncritical acceptance of Western guidelines is inappropriate. The necessity of pharmacologic thrombo-prophylaxis can be answered only from the results of the prospective study on the incidence of postoperative VTE development after gastric cancer surgery. Moreover, current surgical trend in cancer patients is minimally invasive approach such as laparoscopic surgery. However, the necessity of pharmacologic thromboprophylaxis in patients receiving laparoscopic cancer surgery has not been evaluated even in Western countries. Western guidelines also cannot exactly answer whether pharmacologic thromboprophylaxis is really necessary in cancer patients receiving laparoscopic cancer surgery. On above backgrounds, this study was designed.