PURPOSE: Hepatocyte growth factor (HGF) is a modulator of epithelial cell proliferation and motility. In this study, we measured the level of HGF in sera and tumor extracts of gastric adenocarcinoma using an enzyme-linked immunoassay and evaluated its association with tumor progression. MATERIALS AND METHODS: The level of HGF in the sera of seventy-five patients with gastric adenocarcinoma and in the tumor extracts of forty-two tumors were examined in this study. The level of HGF was determined by an Immunis HGF EIA kit (Institute of Immunology). RESULTS: The mean level of HGF in the sera of patients was 0.26+/-0.19 ng/ml, which was significantly higher than in those of healthy controls (0.14+/-0.07 ng/ml, p<0.05); the levels of HGF in the sera of patients increased according to the progression of the stage of cancer (p<0.05). The mean level of HGF in tumor extracts was 8.22+/-9.27 microgram/g protein, which was significantly higher than in those of healthy controls (1.95+/-1.45 microgram/g protein, p<0.05); the levels of HGF in the tumor extracts were correlated significantly with the progression of the tumor stage (p<0.05). The mean level of HGF in the tumors of diffuse type was 11.28+/-11.74 microgram/g protein, which was significantly higher than in those of intestinal type (5.16+/-4.31 microgram/g protein, p<0.05). CONCLUSION: HGF may play an important role in the progression and differentiation of gastric adenocarcinoma.