BACKGROUND During the last two decades, a rising incidence of adenocarcinoma of the esophagus has been observed in the Western world. The prognostic relevance of tumor-biological factors, such as DNA ploidy or c-erbB-2 overexpression, for overall survival following complete resection is still unknown. METHODS In a retrospective study of 80 patients with adenocarcinoma of Barrett's esophagus, the prognostic significance of flow cytometric DNA ploidy determination was investigated. Overexpression of c-erbB-2 oncoprotein was studied by immunohistochemical alkaline phosphatase-antialkaline phosphatase staining of formalin fixed, paraffin embedded tissue sections of the primary tumor. RESULTS The rate of aneuploidy was 86%. Aneuploidy was significantly correlated with lymph node metastases only. c-erbB-2 oncoprotein overexpression of the primary tumor was detected in 15 patients (19%). A significant correlation was seen between c-erbB-2 overexpression and depth of tumor invasion, lymph node involvement, distant metastases, and status of residual tumor after resection (R category, International Union Against Cancer [UICC], 1987). All primary tumors with c-erbB-2 oncoprotein overexpression were aneuploid. In a multivariate Cox regression analysis for overall survival of those 62 patients (78%) whose tumor resection was macroscopically and microscopically complete (R0-UICC), depth of invasion, distant metastases, and c-erbB-2 overexpression were independent prognostic factors. The relative risk of death due to recurrence was nearly identical for patients with either c-erbB-2 oncoprotein overexpression or distant metastases: 4.06 (1.4-11.8) and 3.94 (1.6-9.5). In a multivariate Cox regression analysis of the subgroup of lymph node-negative patients (n = 26), the ploidy status of the primary tumor (defined as near-diploid plus tetraploid versus aneuploid plus multiploid) was the only independent prognostic factor for overall survival. CONCLUSIONS These findings demonstrate that DNA ploidy as well as c-erbB-2 oncoprotein overexpression are valuable prognostic factors in patients with adenocarcinoma of Barrett's esophagus after complete tumor resection.