DNAs from 37 human gastric carcinomas and seven lymph node metastases were analyzed for alterations of the epidermal growth factor receptor (EGFR) gene and oncogenes by the Southern blot hybridization method. The probes used were EGFR gene, c-Ha-ras, v-Ki-ras, N-ras, c-myc, v-myb, v-fos, c-erbB-2, v-erbA, v-abl and v-fes. Amplification of the EGFR gene was detected in only one poorly differentiated adenocarcinoma. Amplifications of c-myc gene and c-erbB-2 gene were each observed in two well differentiated adenocarcinomas. One of these tumors had coamplification of c-erbB-2 and c-erbA genes but there were no amplifications nor rearrangements of other oncogenes. The poorly differentiated adenocarcinom with amplified EGFR gene also showed enhanced expression of EGFR gene by Northern blot analysis and additionally had strong synchronous immunoreactivity for EGFR and EGF.