PURPOSE:The extent of lymph node dissection optimal for the prognosis of right colon cancer is investigated.METHODS:Between 1946 and 1991, 275 patients had curative operation for right colon cancer. A retrospective analysis of rate and degree of lymph node metastasis was performed in each of the 275 patients, and survival rate was estimated in 197 patients who could be followed over a period of three years or more.RESULTS:In most of the curative operative cases of right colon cancer, metastasis to epicolic and paracolic nodes was restricted up to 10 cm proximal or distal to the tumor margin, and metastasis in the central direction was restricted up to main nodes. When cancer metastasized to infrapyloric lymph nodes, dissection of the nodes resulted in a higher rate of long‐term prognosis. The five‐year cumulative survival rates showed no statistically significant difference between any two of the N0 to N3 lymph node metastasis groups.CONCLUSION:The dissection procedure for right colon cancer involved removal of 10 cm of normal bowel both proximal and distal to the lesion and, in the central direction, dissection of regional lymph nodes along the main trunk artery up to main nodes,i.e.,nodes situated anterior to the surgical trunk, which was confirmed to have a therapeutically satisfactory benefit. Infrapyloric lymph nodes must be dissected when metastasis to the nodes is suspected. In cases of cecal or ascending colon cancer in which the middle colic artery is no longer the main trunk artery, a right hemicolectomy with resection of only the right branch of the middle colic artery will usually suffice.