The goal of this study was to identify a set of fluorescence in situ hybridization probes for the detection of dysplasia and adenocarcinoma in patients with Barrett's esophagus. We examined 170 brushing specimens from 138 patients with Barrett's esophagus or a history of Barrett's esophagus using fluorescence in situ hybridization with probes to 5p15, 5q21-22, centromere 7, 7p12, 8q24.12-13, centromere 9, 9p21, centromere 17, 17p13.1, 17q11.2-12, 20q13.2, and centromere Y. Receiver-operator curves were used to determine the sensitivity and specificity of various four-probe combinations for detecting low-grade dysplasia, high-grade dysplasia, and esophageal adenocarcinoma. Endoscopic biopsy results were used as the gold standard. Numerous four-probe combinations provided a similarly high sensitivity and specificity. Of these, a set consisting of probes to 8q24, 9p21, 17q11.2, and 20q13.2 was found to have a sensitivity and specificity, respectively, of 70% and 89% for low-grade dysplasia, 84% and 93% for high-grade dysplasia, and 94% and 93% for esophageal adenocarcinoma. This probe set was chosen for future prospective clinical evaluations based on its high sensitivity and specificity, its ability to distinguish adenocarcinoma and high-grade or low-grade dysplasia from lesser diagnostic categories, and the favorable signal quality for each of the probes.