Although colorectal cancer (CRC) is one of the common cancers and the incidence is rapidly increasing in Asia, there have been few prospective data on the incidence of VTE development during the postoperative period in Asian CRC patients. To our knowledge, there have been a few small-sized prospective studies in Asia and thus clear conclusions could have not been drawn based on those studies. Most Korean colorectal surgeons think that the incidence of postoperative VTE development is very rare based on their own clinical experiences. 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, many Korean colorectal surgeons do not perform perioperative pharmacologic thromboprophylaxis using LMHW. Considering these clinical situations in Asia including Korea, the uncritical acceptance of Western guidelines may be inappropriate. The necessity of pharmacologic thrombo-prophylaxis can be answered only from our own prospective study on the incidence of postoperative VTE development after CRC 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.