852A is an immune response modifier being developed by 3M Pharmaceuticals. It is thought to exert its therapeutic effect by simulating alpha interferon. 852A is similar to the immune response modifier imiquimod(Aldara). Imiquimod is presently approved by the precancerous dermatological condition, actinic keratosis. It is very effective. Treatment is simply applying 5% imiquimod cream twice weekly to the skin lesion for 16 weeks. It seems reasonable that if an immune response modifier will eliminate precancerous lesions of the skin by local application, the same should be true for precancerous lesions of the esophagus. In this study 852A will be swallowed to see whether it can eliminate high grade dysplasia from the esophagus.