Background/Aims: The p53 gene is a tumor suppressor gene that inhibits carcinogenesis. In colonic neoplasms, p53 mutation was reported in many studies, but conventional PCR-SSCP protocol using radioisotopic PCR primer or nucleotides to generate radioactive PCR products is cumbersome to handle. In a previous study, we reported a rapid and safe method for detecting p53 mutation using PCR products by modified cold SSCP (mini-SSCP) method to detect the p53 mutation in gastric cancers, In this study, we applied this method to detect p53 rnutation in colon polyps and cancers and to find the relationship between p53 mutation and clinicopathologic parameters. Methods: We investigated p53 mutation in adenomas and carcinomas of the large bowel by modified cold SSCP and silver sequencing. The cases studied included 28 adenomas and 40 colorectal carcinomas. Results: p53 mutation was noted in 25% of twenty-eight adenomas and in 58% of forty carcinomas. In colorectal adenomas p53 mutation was not related with pathologic type of adenomas but related with adenoma size. In colorectal carcinomas p53 mutation was not related with relevant clinicopathologic parameters, including disease stage and tumor differentiation. In using silver sequencing, the most frequent site of p53 mutation was exon 5 and the most frequent abnormality of DNA sequencing was insertion in colonic neoplasm. Conclusions: Our data suggest that p53 mutation may play an important role in late stage of adenoma-cancer sequence and is related with tumor size. (Korean J Gestroenterol 1998; 31: 47-57)