Ragweed (Ambrosia spp.) is awell-recognised cause of fall allergic rhinitisand seasonal asthma in the Northern Hemispherecountries of United States and Canada. InAustralia the appearance of ragweed (Ambrosia artemisiifolia) was first recordedduring the 1930s in Queensland, ragweed hayfeverwas noted in 1959 and ragweed dermatitisdocumented in 1963. Aerobiology studies performedin the capital cities of Eastern and WesternAustralia have not demonstrated ragweed pollen.This study, performed in two towns in theNorthern Rivers area of New South Wales, closeto the Queensland border, documents the ragweedseason between November 1996 and December 1997in one of the towns, by monitoring the air usinga Burkard 7-day spore trap. Two hundred and sixvolunteers were skin tested to a range ofaeroallergens including pollen of ragweed (Ambrosia artemisiifolia) and Tibouchina, a treeflowering at the same time as ragweed. 34% ofvolunteers were skin prick test positive toragweed and 5.4% to Tibouchina. The ragweedseason commenced in the first week of March andextended to early May, with the peak day pollencount, 483/m3, present in the first week ofApril. Although many residents blamed thespectacular purple Tibouchina flowers for latesummer respiratory symptoms, most were sensitiveto ragweed and not Tibouchina.