Kisspeptins, which are derived from the gene KISS1, supress tumor progression. We intended to investigate the production of KISS1 and its receptor (KISSR) in gastric cancer.The expression of KISS1 and KISS1R in both normal and cancer tissue was examined with immunohistochemistry in tissue specimens of 40 cases of gastric adenocarcinoma.KISS1 expression in normal gastric mucosa was much higher than in malignant mucosa. KISS1 expression was higher in early stages (stage I or II) than in advanced stages (stage III or IV), in tumors with intestinal histological type than in those with diffuse histological type, in tumors without lymphovascular invasion than in those with and in cancers of older patients (≥70 years) than in younger patients. No significant differences were found regarding other clinicopathological parameters. There was no KISS1R expression in cancer tissues, while only low levels of KISS1R were detected in normal gastric epithelium.KISS1 expression is decreased during carcinogenesis in gastric mucosa. More advanced tumors and more aggressive histological types produce lower KISS1 levels. In addition, no KISS1R is produced in malignant gastric epithelium, while KISS1R is only weakly expressed in normal gastric epithelium.