Homeopathy is considered as one modality for cancer therapy. However, there are only very few clinicalreports on the activity of the drugs, as well as in experimental animals. Presently we have evaluated the inhibitoryeffects of potentized homeopathic preparations against N’-nitrosodiethylamine (NDEA) induced hepatocellularcarcinoma in rats as well as 3-methylcholanthrene-induced sarcomas in mice. We have used Ruta, Hydrastis,Lycopodium and Thuja, which are commonly employed in homeopathy for treating cancer. Administration ofNDEA in rats resulted in tumor induction in the liver and elevated marker enzymes such as gamma-glutamyltranspeptidase, glutamate pyruvate transaminase, glutamate oxaloacetate transaminase and alkaline phosphatasein the serum and in liver. Concomitant administration of homeopathic drugs retarded the tumor growth andsignificantly reduced the elevated marker enzymes level as revealed by morphological, biochemical andhistopathological evaluation. Out of the four drugs studied, Ruta 200c showed maximum inhibition of livertumor development. Ruta 200c and phosphorus 1M were found to reduce the incidence of 3-methylcholanthreneinducedsarcomas and also increase the life span of mice harboring the tumours. These studies demonstrate thathomeopathic drugs, at ultra low doses, may be able to decrease tumor induction by carcinogen administration. Atpresent we do not know the mechanisms of action of these drugs useful against carcinogenesis.