【Abstract】 Objective To investigate the incidence of P53 and K-ras gene mutation in colorectal adenomas and primary colorectal carcinomas. Methods There were 25 normal samples, 38 samples of colorectal adenoma, 78 samples of single primary colorectal cancer and 19 samples of multiple primary colorectal carcinomas (7 synchronous colorectal carcinomas and 12 metachronous colorectal carcinomas) collected in this study. With the analysis of clinico-pathologic features for each patient, exon 5-8 of P53 gene and codon 12-13 of K-ras gene of each sample were extended by real-time PCR. Multi-factor correlation analysis was carried out between the clinicopathologic features and the mutation of P53 and K-ras gene in colorectal adenoma and primary colorectal cancer. Results The P53 gene mutation is 0% (0/25)，44.8%（17/38），43.6%（34/78）and 42.1%（8/19）respectively in normal mucosa tissue, colorectal adenomas, single lesion and multiple lesion of primary colorectal carcinomas, while the proportion of K-ras gene mutation was 0%（0/25），18.4%（7/38），39.7%（31/78），47.4%（9/19）respectively. In our investigation there were obvious statistical differences as to the proportion of mutation of the P53 and K-ras gene between normal mucosa tissue and other three groups respectively (P
