Even in the 21st century, despite tremendous advances in the synthetic medicinal chemistry, plants are considered an integral part of the health care system in many countries of the world.This phenomenon is based not only to the traditions of folk medicine in different civilizations but also on the fact that medicinal plants have a leading position in drug discovery.In an attempt to screen the medicinal herbs from the Jordanian flora, more than 100 ethanolic, chloroform and water extracts belonging to about 45 families representing 80 genera were evaluated for their antiproliferative activity on a breast cancer cell line (MCF7).The cells were cultured in RPMI 1640 mediuan and incubated with the extracts for 72 hours.Sulphorhodamine B (SRB) assay was used to test cytotoxicity.From the tested crude extracts for MCF7 cells, Inula graveolens, I.viscosa, Salvia dominica, S.syriaca, Conyza canadiensis and Achillea santolina showed potent antiproliferative activities.The most active plant wasI.graveolens with an IC5o of 3.83μg/ml.The ethanolic extracts of the active plants were further evaluated using T47D, ZR-75-1 and BT474 cell lines.Phytochemical screening of these plants indicated the presence of flavonoids and terpenoids in all active extracts.Therefore, some of the volatile fractions obtained from the active plants as well as the isolated pure flavonoids have been also tested for their antiproliferative activities using MCF7 cells.The obtained results from the present study indicate the possible potential use of medicinal plants from the Jordanian flora as antineoplastic agents.