The caspases are a family of aspartic acid-specific proteases that fulfill varied and often critical roles in mammalian apoptosis or in the proteolytic activation of cytokines. Caspase-1 (interleukin-1beta-converting enzyme) is a member of the cysteine protease family, which cleaves target proteins following aspartic acid residues. We investigated caspase-1 expression in stomach cancer, tissues and cell lines. Of 301 consecutive gastric carcinomas, 58 cases (19.3%) showed the expressional loss of caspase-1. Loss of caspase-1 expression was significantly associated with pTNM stage (p=0.03), lymph node metastasis (p=0.01) and patient survival (p<0.01). Caspase-1 expression was also significantly correlated in an inverse manner with p53 expression (p<0.01). Among the 11 gastric cancer cell lines examined, three cell lines showed loss of expression at the protein and mRNA levels. On treatment with 5-aza-2'-deoxycytidine (5-aza-C), and/or trichostatin A (TSA), all three cell lines re-expressed caspase-1 mRNA. The above findings suggest that epigenetic events such as DNA methylation and histone deacetylation play important roles in the regulation of caspase-1, and that loss of caspase-1 expression is associated with poor survival in gastric carcinoma.