Cancer is a disease that begins in the cells of the body. Side effects of allopathic drugs and development of resistance to currently used drugs for infectious diseases have led to increased emphasis on the use of plant materials as a source of medicines for a wide variety of human ailments The compounds derived from plants and their semi-synthetic as well as synthetic analogs have been important source of several clinically useful anti-cancer agents. Some of them include vinblastine, vincristine, shatavarin VI, pollen tripdecapeptide PSPP3, essential oils, etoposide and paclitaxel. In the cancer drug discovery program, a paradigm based on ethnobotanical and ethnopharmacological data would be more economic and beneficial for identifying potential anti-cancer molecules than mass screening of plants species. With the advent of combinatorial chemistry and high throughput screening, however, even greater progress may be expected with natural product leads.A number of promising new agents are in clinical development based on selective activity against career related molecular targets. This paper deals with some important medicinal plants used as an anti-cancer activity.