The pollen of Ambrosia (ragweed) is one of the major causes of pollen-induced allergy worldwide. This family of plants has apparently evolved in North America but was later spread into Europe and Asia. Flowering of the Ambrosias starts in mid-July and continues throughout the autumn and is a cause of major morbidity to allergic sensitized patients. The invasion of new species of Ambrosia into Israel is still in progress. Plants of Ambrosia artemisiifolia (American short ragweed), Ambrosia trifida (American giant ragweed), Ambrosia confertifolia, Ambrosia grayi and Ambrosia tenuifolia are increasingly found in Israel, mainly in the Hula valley in the eastern Galilee and near the Alexander River in the Sharon plain. From experience it is known that the time it takes to eradicate a new invasive species is limited. Action should be taken immediately or this new invasion will spread and cause a significantly increased burden of morbidity and increased health costs in Israel.