Peritoneal dissemination can be prevented by the responsible surgeon at least in part by proper surgical technique used to resect the primary malignancy. What most people do not know is that cancer surgery can do great harm. It can convert a contained malignant condition into a disseminated disease that unnecessarily becomes a deadly process. Containment must be the number one priority of the gastrointestinal cancer surgery. Also, established peritoneal carcinomatosis can be cured if it is attacked in a timely fashion with peritonectomy procedures and heated intraoperative intraperitoneal chemotherapy. Many small changes can make a big difference in survival with gastrointestinal cancer surgery. (J Nippon Med Sch 2000; 67: 5-8)