Esophageal cancer is one of the 10 most prevalent human cancers worldwide. The incidence of esophageal adenocarcinoma is on the rise and patients with this disease typically have very poor prognosis. Informative biomarkers would benefit the clinical management of this disease. We examined 13 cases with esophageal adenocarcinomas and 5 cases with Barrett's esophagus for amplification of the EGFR and erbB-2 genes. We detected multiple copies of the EGFR gene in 30.8% of the tumors and multiple copies of the erbB-2 gene in 15.4% of the tumors. Of the cases with amplification of the erbB-2 gene, co-amplification of the EGFR gene was found. Multiple copies of the EGFR gene were also found in one case of Barrett's esophagus. Immunohistochemical staining of the tissues revealed increased expression of the erbB-2 protein in Barrett's mucosa and adenocarcinoma, but no associations between staining intensity and degree of EGFR or erbB-2 gene amplification, histology, or tumor stage were found. Differential polymerase chain reaction was examined as a method for pre-operative detection of gene amplification in esophageal tumors and Barrett's mucosa.