Anticarcinogenic effect of red ginseng (Panax ginseng C.A. Meyer cultivated in JiLin, China) on the development of liver cancer induced by diethylnitrosamine (DEN) in rats was studied, especially in preventive and curative groups. In the preventive group, the rats were given with DEN concomitantly with red ginseng fluid, and in the curative group, the rats were administered with red ginseng fluid after they developed liver cancer nodules induced by DEN. The result of the preventive group revealed that the developmental rate of liver cancer in the experimental group was 14.3%, while 100% in the control group, with the difference being statistically significant. DNA, RNA, glycogen, gamma-GT, SDH, and 5'-NT were maintained at relatively normal level in experimental group, and decreased or increased in the control group. The result of curative group showed that hepatoma nodules of the DEN-red ginseng group I were smaller than those of control group I, the structure of hepatic tissue was well preserved, the area with gamma-GT positive was smaller, and the ultrastructure of hepatocytes was normal. The average life span the DEN-red ginseng group II and the DEN control group II were 72.8 and 42.3 days, respectively. To sum up, all findings on preventive and curative groups had clearly proved that the red ginseng had the anticarcinogenic effect on the development of liver cancer induced by DEN in rats.