Abstract: The Chinese drug "Shan - Dou- Gen" has been used for removing toxicheat, promoting the subsidence of swelling and soothing the sore throat since the ancienttime. The authors made a survey of the durg "Shan-Dou-Gen" available in drug marketsas well as the plant origin from the drug producing districts. The results showed that thedrug "Shan-Dou-Gen" used in different regions in China at present are the roots orrhizomes derived from 9 species: Sophora tonkinensis Gagnep. (Leguminosae),Menispermum dauricum DC. (Menispermaceae), Indigofera amblyantha Craib(Leguminosae), I. carlesii Carib, I. fortunei Craib, I. decoa Lindl. var.ichangensis Y. Y. Fang et C. Z. Zheng, I. kirilowii Maxim. et Palibin, I. potaninii Craib, and Beesia calthaefolia (Maxim.) Ulbr. (Ranuculaceae). In this paper, themorphological characters of the crude drugs are described, compared and illustrated withphotographs. The histological structures of the used parts are described, compared and il-lustrated with line drawings. The morphlolgical and histological similarities and differences found among the above9 species are summarized, and the key for the identification of the crude drugs is provid-ed. As the drug "Shan- Dou- Gen"derived from different species has different actions anddosages, it is necessary to give different names to different species and use them correctly.