Histopathologic grading of dysplasia in Barrett esophagus (BE) shows substantial interobserver and intraobserver variation. We used immunohistochemical analysis with a set of tumor cell markers, ie, epidermal growth factor receptor (EGFR), ERBB2 (HER2/neu), MYC, CDKN2A (p16), SMAD4, MET, CCND1 (cyclin D1), CTNNB1 (beta-catenin), and TP53 (p53), in histologic sections of endoscopic biopsies of 86 patients with BE in various stages of neoplastic progression. The markers, except SAMD4, were scored as 0 (< 1% of cells stained), 1 (1%-25%), 2 (26%-50%), or 3 (> 50%). All markers, except EGFR, showed a significant trend for immunohistochemical protein overexpression during malignant progression in BE (P < .01). When the successive stages along the metaplasia-low-grade dysplasia (LGD)-high-grade dysplasia (HGD)-adenocarcinoma axis were compared, protein overexpression of P-catenin separated LGD from metaplasia, whereas protein overexpression of cyclin D1 and p53 discriminated HGD from LGD (all P <. 001). beta-Catenin can be helpful for a diagnosis of LGD in BE, although it stains positively in a subset only, whereas p53 remains an appropriate marker to define HGD. In case of doubt, cyclin D1 can be added to separate LGD from HGD in BE.