Abstract: Mucoaa adjacent to colorectal cancer often differs from normal mueoaa in both morphology and histochemiatry. Some reports showed that mucoaas adjacent to cancer were in the state of precancer-oua. We examined Ifi-ras gene mutations in 13 colorectal cancers and their adjacent mucasas by PCR-RFLP. There are 2 cases with ki-raa mutations in both tissues，2 casea with ki-raa muca-lions only in cancer tissue，and 1 case with lei-ras mutation only in mucosa adjacent to cancer. The results show that ki-ras mutations occured in some mucoaaa adjacent to cancer. Which confirm that ki-ras mutation may occur at the early stages of carcinogenesis and development of colorectal can-cars. No distinct relations o! gene alteration exists between cancer and adjacent mucoaa tissues.