Barrett's esophagus with high-grade dysplasia is a premalignant condition caused by chronic reflux of gastric contents into the esophagus. High-grade dysplasia is the same as carcinoma-in-situ. If untreated, patients with this condition are at high risk for developing cancer of the esophagus. Cancer of the esophagus is a miserable disease that is difficult to treat and about 95% fatal after 5 years. To prevent progession to cancer of the esophagus several interventions are available and they include surgery, Photofrin photodynamic therapy, endoscopic mucosal resection and endoscopic thermal therapy. All of these modalities are uncomfortable, expensive and have associated risks. The oral agent, 852A stimulates the innate immune system in such a way as to eliminate early cancer. A similar dermatologic drug(imiquimod) is approved for treating the premalignant condition, actinic keratosis. If local therapy with imiquimod can eliminate a premalignant lesion in the skin, a similar acting drug should be able to do the same for a premalignant lesion in the lining of the esophagus. This study is designed to test that hypothesis.