Adenocarcinomas of the gastro-esophageal junction (GEJ) and those arising in Barrett's esophagus (BE) are increasing in the West and have a poorer prognosis than distal stomach cancers. This has been attributed mainly to anatomical location, but biological factors such as growth-regulatory molecules have been implicated. We have investigated the expression of one of these factors, TGF alpha, and its precursor prepro TGF alpha in 82 adenocarcinomas of GEJ (32 resected specimens and 50 biopsies) as well as in 48 BE biopsies without tumor, by immunohistochemistry and by Western-blot analysis. TGF alpha staining was shown in the cytoplasm and membrane of cells. Western blot confirmed that most immunoreactivity was against mature TGF alpha (5.6 kDa), but higher-molecular-weight bands were also identifiable, suggesting some reactivity with prepro protein. TGF alpha expression was more extense and intense in intestinal metaplasia and cancer. The tubular histological type of adenocarcinoma was more often positive than the signet-ring type. Primary tumors with lymph-node metastases also had increased TGF alpha expression. We conclude, therefore, that there is differential regulation of the expression of TGF alpha and its precursors during esophageal tumorigenesis.