In this report, 648 cases of marked epithelium hyperplasia diagnosed with esophageal exfoliative cytology were studied clinically in the high incidence areas (Cixian and Shexian) of esophageal cancer. All these cases were randomly divided into the treated group and the control group. For two years, the former had been given Cang Dou Pill and the latter the placebo. The results reexamined by the cyto-smears showed that the incidence of the esophageal cancer in therapeutic and control group were 1.5% and 4.2% respectively. A significant difference existed between the two groups (P < 0.005). And the reverse rate of marked hyperplasia in the treated and control group were 79.5% and 50.2% respectively. There was significant difference between the two groups (P < 0.01). These results showed that Cang Dou Pill, to some extent, has anti-cancer activity.