C-erbB-2 (HER-2/neu) proto-oncogene is mainly expressed in epithelial tissue and activated due to its amplification. Amplification of the C-erbB-2 proto-oncogene is associated with poor prognosis in human ovarian cancer. We examined whether amplification of C-erbB-2 is common in ovarian carcinoma or is associated with poor prognosis. The DNA of ovarian carcinoma was extracted and consequently digested with restriction endonuclease EcoRI, electrophoresed in 0.8% agarose gels and blotted onto nitrocellulose filter with Southern transfering method. It was hybridized with a 32p-labelled C-erbB-2 probe and subsequently underwent autoradiography. It was shown that the C-erbB-2 (HER-2/neu) gene was amplified in 8 of 26 human ovarian carcinomas (30.8%). Clinically the 8 patients with the amplified C-erbB-2 were in their advanced stage (III-IV). Five of the patients died from 2 to 4 months after operation. These findings suggest that amplification of the C-erbB-2 gene may play a role in the pathogenesis of ovarian carcinoma, it is frequently observed in advanced ovarian carcinoma and associated with poor prognosis for these patients.