Overexpression of human epidermal growth factor receptor 2 protein (Her-2) in Barrett neoplasia is significant for targeted therapy with trastuzumab. Here, we studied the frequency of Her-2 overexpression in Barrett adenocarcinoma and precursor lesions. Retrospective formalin-fixed paraffin-embedded tissue samples of 25 normal (NM) esophageal mucosa, 50 Barrett esophagus (BE) without dysplasia, 49 BE with low-grade dysplasia (LGD), 50 BE with high-grade dysplasia (HGD), and 50 invasive adenocarcinoma (ICA) were used. A BE tissue microarray was built and analyzed by Her-2 immunohistochemistry (IHC) and Her-2 dual in situ hybridization (DISH). Her-2 IHC expression was negative in NM and low in 26% of BE (IHC score: 1+) and in 24.5% of LGD (IHC score: 1 to 2+). Her-2 overexpression was seen in 28% of HGD and in 24% of ICA (IHC score: 2 to 3+). Her-2 DISH was negative in NM and BE but positive in 6% of LGD, 20% of HGD, and 18% of ICA. Differences in Her-2 DISH positivity between NM and HGD or ICA were statistically significant (P=0.02), but those between NM and LGD or HGD and ICA were not (P=0.2). Although Her-2 overexpression results in ICA were similar to previous reports, the finding of 28% in HGD was unexpected and may have clinical implications. Positive Her-2 DISH in 6% of LGD is novel, suggesting a role of Her-2 during BE progression.