In 1983, for the purpose of prevention fromesophageal cancer, inhibitory therapy was put ontrial in Heshunxiang of Linxian (County), a high in-cidence area of esophageal cancer in China, to blockcancerous changes in the esophageal precancerouslesions, with an expectation of cutting down thecancerous change rate of severe esophageal dysplasiaby 50%. 6758 inhabitants aged 40-65 were examinedby exfoliative cytology, 1728 and 2412 cases of severeand mild esophageal dysplastic patients were screen-ed out. The former cases were randomized into 3groups, to which antitumor B (Chinese herbs), re-tinamide I and placebo were given respectively. Themild dysplastic patients were randomly divided into2 groups, to which riboflavin and placebo were givenrespectively. Medication rate was over 90%. Eso- In 1983, for the purpose of prevention fromesophageal cancer, inhibitory therapy was put ontrial in Heshunxiang of Linxian (County), a high in-cidence area of ​​esophageal cancer in China, to blockcancerous changes in the esophageal precancerouslesions, with an expectation of cutting down Thecancerous change rate of severe esophageal dysplasiaby 50%. 6758 inhabitants aged 40-65 were examined by exfoliative cytology, 1728 and 2412 cases of severeand mild esophageal dysplastic patients were screen-ed out. The former cases were randomized into 3groups, to which antitumor B ( Chinese herbs), re-tinamide I and placebo were given respectively. The mildly dysplastic patients were randomly divided into 2 groups, to which riboflavin and placebo were given relevantly. Medication rate was over 90%. Eso-