Objective: we investigated the relationship between the expression of Caspase-3. cell proiferation 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-67immunostaining and apoptosis was evaluated using DNA fragmentation in situ by TdT-mediated dUTP biotin nick end label-ing (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 TU-NEL, 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 0.05). 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.