Objective To investigate the relationship between the p33 ING1b protein expression and differentiated degree in human gastric carcinoma. Methods p33 ING1b protein expression was detected by S-P immunohistochemical method in gastric carcinoma and normal gastric mucous tissues. Results The positive rates of p33 ING1b protein expression were 75% (15/20) in well-differentiated, 55% (11/20) in moderate-differentiated and 15% (3/20) in poor-differentiated gastric carcinoma, respectively. The positive rate of p33 ING1b protein expression in gastric carcinoma was significantly lower than that in normal gastric mucosa (100%, 60/60) (P