We examined mRNA expression for c-met encoding hepatocyte growth factor receptor in 8 gastric carcinoma cell lines and 31 surgically resected gastric carcinoma tissues by Northern-blot analysis. Two forms of the transcript, sized 7.0 kb and 6.0 kb, were found in gastric carcinomas. Transcripts of both sizes were detected at various levels in all the gastric carcinoma cell lines except the MKN-74 line, which expressed only the 7.0-kb form. Of the 31 gastric carcinomas, 15 (48%) over-expressed the 7.0-kb transcript when compared with non-neoplastic mucosa. The 6.0-kb transcript of the c-met gene was expressed at considerable levels in 52% of the gastric carcinoma tissues, whereas it was only slightly expressed in non-neoplastic mucosa of a small number of cases. An important finding was that expression of the 6.0-kb transcript was closely correlated with tumor staging, lymph-node metastasis and depth of tumor invasion. These results, overall, suggest that the 6.0-kb transcript of the c-met gene might participate in the development and progression of gastric carcinomas.