Purpose:To investigate the expression of PCNA、p53、C erbB 2 in colorectal carcinoma and its relationship with host immune reactions. Methods:The expression of PCNA、p53、C erbB 2 was detected by Envision immunohistochemical method in 42 colorectal carcinoma, 35 pericarcinomatous and 10 normal coloerctal mucosa respectively. Host immune reactions (pericarcinomatous fibrosis, mononuclear infiltration and lymph nodes reaction) were also observed. Results:(1) The positive expression of PCNA、p53、C erbB 2 in colorectal carcinoma was significantly higher than in corresponding pericarcinomatous mucosa and normal colorectal mucosa respectively( P 0.05). (3) GH was more evident than PH in colorectal carcinoma and GH had reverse relationship with lymph node metastasis( P