OBJECTIVE:To detect and investigate the differences in the expression of C/EBP homologous protein (CHOP) in colorectal adenoma-carcinoma tissue sequences of the same genetic background and its relationship with the cell proliferation/apoptosis ratio (PAR). Methods: Surgical resection specimens of 23 patients with three histological types of colorectal tumors (adenoma with low-grade intraepithelial neoplasia, adenoma with high-grade intraepithelial neoplasia and adenocarcinoma) and their corresponding normal intestinal mucosa were collected, and the expression level of CHOP and the proliferation index (PI) (i.e., the rate of Ki-67-positive cells) were measured by the immunohistochemistry method (SABC); the cell proliferation/apoptosis ratio (PAR) in this tissue specimen was detected by TUNEL method. The apoptotic index (AI) was detected by TUNEL method. Results: (1) Under the same genetic background, the positive cell rate of CHOP in colorectal adenocarcinoma tissue was significantly higher than that in adenoma with high-grade intraepithelial neoplasia, adenoma with low-grade intraepithelial neoplasia and normal intestinal mucosa (p<0.01); the positive cell rate in adenoma with high-grade intraepithelial neoplasia was significantly higher than that in adenoma with low-grade intraepithelial neoplasia and normal intestinal mucosa (p<0.01); the positive cell rate in adenoma with low-grade intraepithelial neoplasia was significantly higher than that in adenoma with high-grade intraepithelial neoplasia and normal intestinal mucosa (p<0.01). The positive cell rate was significantly higher in adenomas with low-grade endothelial neoplasia than in normal intestinal mucosa (p<0.01); (2) under the same genetic background condition, the positive cell rate of par in colorectal adenocarcinomas was significantly higher than that in adenomas with high-grade endothelial neoplasia (p<0.01), low-grade endothelial neoplasia adenomas, and normal intestinal mucosa (p<0.01); and the positive cell rate of par in adenomas with high-grade endothelial neoplasia was significantly higher than that in adenomas with low-grade endothelial neoplasia and normal intestinal mucosa (p<0.01). Adenomas with high-grade intraepithelial neoplasia were significantly higher than those with low-grade intraepithelial neoplasia and normal intestinal mucosa (p<0.01); adenomas with high-grade intraepithelial neoplasia were significantly higher than those with low-grade intraepithelial neoplasia and normal intestinal mucosa (p<0.01); and adenomas with low-grade intraepithelial neoplasia were significantly higher than those with low-grade intraepithelial neoplasia and normal intestinal mucosa (p<0.01). CONCLUSION: In this experiment, we investigated the relationship between CHOP and PAR in colorectal adenoma-cancer tissues of the same genetic background; with the progression of colorectal adenoma cancer, CHOP expression level and PAR gradually increased, and both of them were positively correlated, and CHOP and the abnormalities of cell proliferation and apoptosis might be jointly involved in the process of colorectal adenoma cancer.