Gastrin is one of the most important gut-related hormones contributing to gastric acid secretion. Gastrin and the gastrin receptor (GR) are coexpressed in many gastrointestinal cancer cell lines, and gastrin is regarded as an autocrine growth factor for these cells. Thus, gastrin is important in the investigation of gastrointestinal carcinogenesis and anticancer therapy. The GR (identical with the cholecystokinin B receptor; CCKBR ) gene was cloned by Lee et al. and has an open reading frame encoding 447 amino acids with 7 transmembrane domains. To date, many studies have revealed the localization of GR in the human stomach. It has been of public interest to investigate the expression and potential role of gastrin and GR in gastric carcinogenesis and their relation to Helicobacter pylori infection and inflammation.