Ninety pairs of normal and tumour tissue DNAs were isolated from paraffin-embedded blocks of advanced oesophageal carcinoma cases and examined for gene amplification at chromosome 11q13 by dot-blot hybridisation using the int-2 gene as a probe. 22 of 90 carcinomas (24%) showed more than two times amplification. Although no significant correlation was observed between gene amplification and histological type or metastasis to lymph node, a tendency for deeper invasion to be associated with more frequent amplification was observed. In relation to prognosis, patients with amplification had a lower survival rate than those without amplification. This tendency was evident both in the group with well differentiated type carcinoma and in the group which had no metastasis to lymph node. Thus, gene amplification of the int-2 locus may be a useful prognostic factor.