Abstract: Objective 　To investigate the role of APC, β-catenin and c-myc in the carcinogenesis and progression of colorectal carcinoma. Methods 　Expression of APC, β-catenin and c-myc proteins was examined immunohistochemically in 30 cases of normal colorectal mucosa, 30 cases of colorectal adenoma, 10 cases of colorectal adenoma carcinogenesis and 50 cases of colorectal carcinoma. Results 　The positive expression rates of APC were 44. 0 % and 40. 0 % respectively in colorectal carcinoma and colorectal adenoma carcinogenesis, and both of the rates were significantly lower than that of colorectal adenoma (86. 7 %) and normal colorectal mucosa (100 %) ( P < 0. 01) . The cytoplasmic and/ or nuclear β-catenin expression rates were 62. 0 %, 50. 0 % and 30. 0 % respectively in colorectal carcinoma, colorectal adenoma carcinogenesis and colorectal adenoma, and all of the rates were significantly higher than that of normal colorectal mucosa (0) ( P < 0. 01) . The cytoplasmic and/ or nuclearβ-catenin expression rate in colorectal carcinoma was significantly higher than that of colorectal adenoma ( P < 0. 01) . The positive expression rates of cmyc were 56. 0 %, 60. 0 % and 46. 7 % respectively in colorectal carcinoma, colorectal adenoma carcinogenesis and colorectal adenoma, and all of the rates were significantly higher than that of normal colorectal mucosa (0) ( P < 0. 01) . The reduced membranousβ-catenin expression rate in colorectal carcinoma was significantly higher than that of colorectal adenoma and normal colorectal mucosa ( P < 0. 01) . The reduced membranousβ-catenin expression was closely related with the tissue differentiation degree, the depth of invasion, lymph node metastasis and Dukes stage in colorectal carcinoma. The expression of APC was closely related with the tissue differentiation degree in colorectal carcinoma. The cytoplasmic and/ or nuclearβ-catenin expression was thus in positive correlation with the expression of c-myc ( r = 0. 63, P < 0. 01), and was in negative correlation with the expression of APC ( r = - 0. 39, P < 0. 05 ) . Conclusion 　The reduced cytoplasmic APC expression, the cytoplasmic and/ or nuclear β-catenin expression, and the overexpression of c-myc may play a pivotal role in carcinogenesis and progression of colorectal carcinoma, and may be an early event . The reduced membranousβ-catenin expression may be related to the invasion and metastasis of colorectal carcinoma.