Abstract: The expression of pancreatic cancer-related antigen PS-4 was investigated in 117 gastrectomy specimens of gastric caner and 343 biopsy specimens of intestinal metaplasia by immunohistochemical technique. Among the 117 cases of gastric cancer, 93 (79.5%) showed the positive reaction for PS-4 antigen, while no positive reaction was found in normal gastric mucosa. Intestinal metaplasia was classified into types Ⅰ, Ⅱ and Ⅲ by histochemical mucin stainings. In different types intestinal metaplasia, type Ⅲ exhibited a significantly higher positive rate for PS-4 antigen than types Ⅰ and Ⅱ (P0.01), suggesting that typa Ⅲ intestinal metaplasia is cioseiy related to the histogenesis of gastric cancer. Our results indicate that PS-4 antigen may be valuable tumor marker in detecting gastric cancer and defining the highrisk group of gastric cancer.