Abstract: Objective: To explore the expression of p33^ING1 in colorectal cancer and its correlation between the clinic pathological features and the possible mechanism of p33^ING1 in the oncogenesis of colorectal neoplasms.Methods: Sixty histological verified colorectal carcinomas and twenty neighboring no cancerous tissues were obtained.Immunohistochemistry staining was used to detect p33^ING1 and p21^WAF expression in colorectal carcinomas and normal tissues.Results: p33^ING1 expression were detected in 26 of 60(43.3%) in colorectal carcinoma,and p33^ING1 expression were detected in 18 of 20(90.0%) in neighboring no cancerous tissues;A significant decrease in p33^ING1 expression was found in colorectal carcinomas(P<0.005).The result also showed that expression of p33^ING1 markedly related to both the Dukes classification and metastasis(P<0.005 and P<0.01);and was not related to patient's sex,age,tumor differentiation,site and tumor growth(P>0.05).The relationship between p33^ING1 and p21^WAF was positive correlation(P<0.05).Conclusions: p33^ING1 expression in colorectal carcinoma is low,and plays an important role in the colorectal carcinogenesis and development.The p33^ING1 and p21^WAF expression can be used as one of the important indicators for level of malignancy in colorectal carcinomas.