To elucidate further genetic alterations in flat-type colorectal tumors, codon 201Arg/Gly polymorphism in the DCC (deleted in colorectal carcinoma) gene was analyzed in normal tissue (normal colonic mucosa or peripheral lymphocytes) and in tumor tissue from 191 patients with colorectal tumors (36 patients with flat-type colorectal tumors, 81 patients with polypoid-type colorectal tumors, and 74 patients with advanced carcinomas).