The present study was undertaken to assess the carcinopreventive properties of aqueous extracts of an Indian medicinal plant Indigofera aspalathoides, on 20-Methylcholanthrene induced fibrosarcoma in Wistar strain male albino rats. Fibrosarcoma was induced by subcutaneous implantation of Millipore filter disc impregnated with 5% suspension of 20- Methylcholanthrene in paraffin oil and the tumors appeared in about six weeks. The fibrosarcoma was isolated and proved by histo pathological examinations. Intraperitoneous (i. p.) administration of 250 mg/kg b.w. /day of aqueous extract of Indigofera aspalathoides for 30 days was conducted. The aqueous extract of Indigofera aspalathoides treatment reduced the tumor size and volume in control and experimental animals. The levels of electrolytes such as Na+ , K+ , Ca2+, Mg2+ were analyzed in serum of control and experimental animals and the Na+, K+ ATPases, Ca2+ATP ase and Mg2+ ATPases levels were observed in erythrocyte membrane and liver and kidney of control and experimental animals. The levels of these electrolytes and those of the enzymes were altered significantly in control and experimental animals. Our results clearly indicated the carcinopreventive properties of Indigofera aspalathoides on 20-ethylcholanthrene induced fibrosarcoma in rats.