Objective: We investigated the relationship between the expression of Caspase-3, cell proliferation and apoptosis in gastric cancer and their precancerous lesions, to explore the tumorigenesis of the stomach mucosa. Methods: Caspase- 3 expression in 13 normal gastric mucosa, 6 chronic atrophic gastritis (CAG), 31 intestinal metaplasia (IM), 114 dysplasia (DYS) and 20 gastric carcinomas were investigated immunohistochemically. Cell proliferation was evaluated with anti-Ki-67 immunostaining and apoptosis was evaluated using DNA fragmentation in situ by TdT-mediated dUTP biotin nick end labeling (TUNEL) method. Results: Caspase-3 mild-moderately positive expression was observed in most of normal superficial epithelia, its positively polar distribution in normal mucosa, CAG, IM, DYS and gastric carcinomas changed as seen in TUNEL, and so did the positive rate. Caspase-3 protein expression showed significantly positive correlation with the number of apoptotic cells labeled with TUNEL (correlation coefficient r = 0.94; P < 0.01). Ki-67 expression showed a negative but not significant correlation trend with Caspase-3 (correlation coefficient r = –0.23; P > 0.05). Conclusion: Caspase-3 protein expression was up-regulated from CAG to IM and mild-moderate atypical dysplasia, but down-regulated in severe dysplasia and gastric carcinoma, indicating that inactivity or reduced expression of Caspase-3 is closely correlated with carcinogenesis of the stomach mucosa. Objective: We investigated the relationship between the expression of Caspase-3, cell proliferation and apoptosis in gastric cancer and their precancerous lesions, to explore the tumorigenesis of the stomach mucosa. Methods: Caspase- 3 expression in 13 normal gastric mucosa, 6 chronic atrophic Cell proliferation was evaluated with anti-Ki-67 immunostaining and apoptosis was evaluated using DNA fragmentation in situ by TdT-mediated dUTP (CYS), 31 intestinal metaplasia (IM), 114 dysplasia Results: Caspase-3 mild-moderately positive expression was observed in most of the normal superficial epithelia, its positive polar distribution in normal mucosa, CAG, IM, DYS and gastric carcinomas changed as seen in TUNEL, and so did the positive rate. Caspase-3 protein expression showed significantly positive correlation with the number of apoptotic cells labeled with TUNEL (corre (P <0.01). Ki-67 expression showed a negative but not significant correlation trend with Caspase-3 (correlation coefficient r = -0.23; regulated from CAG to IM and mild-moderate atypical dysplasia, but down-regulated in severe dysplasia and gastric carcinoma, indicating that inactivity or reduced expression of Caspase-3 is closely correlated with carcinogenesis of the stomach mucosa.