PURPOSE: Bombesin-like peptides are known to be important in the autocrine growth of a number of small cell lung cancer cell lines. The aim of this study was to investigate the extent of bombesin family ligands/receptors expression in human gastric cancer tissues and cell lines, and to evaluate the relationship between the expression of bombesin family ligands/receptor and clinicopathologic parameters. METHODS: We measured the expression of gastrin releasing peptide (GRP), neuromedin B (NMB), and their receptors, in human gastric cancer tissues and cell lines. Ligand and receptor mRNA studies were carried out on; 20 tumor and matched normal samples, and 9 gastric cell lines. The expression of mRNA of GRP/NMB, and their receptors, was examined by the reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: Expression of GRP, NMB and GRPR, NMBR mRNA was found in 55%, 100%, 40%, and 100% of gastric cancer tissue, respectively. GRP/GRPR co-expression was observed in 30% of gastric cancer tissues and expression of gastric cancer was higher than that of normal mucosa. GRP and GRPR were highly expressed in the differentiated type of gastric cancer. In gastric cancer cell lines, these peptides and receptors were expressed equally. CONCLUSION: The result demonstrate that GRP, NMB, GRPR, and NMBR were expressed in gastric cancer tissues and cell lines. This result suggests that these may have a role as growth factors in gastric cancer growth, and these peptides may act in an autocrine fashion as a morphogen in gastric cancer.