Niuxi has been used as an important drug in Chinese medicine since ancient times. However, the origins and commercial species of Niuxi are complicated and often misused in Taiwan. Three major species are Achyranthes bidentata B□ (NX-1). Cyathula officinalis K□ (NX-2) and Strobilanthes forrestii D□ (NX-3). According to the Chinese ancient literature of successive generations, Niuxi can quicken the blood and transform stasis, free the channels and hasten birth, disinhibit the joints, strengthen the sinew and bones, supplement the liver and kidney, conduct blood downward, disinhibit water and free strangury. These indications imply that Niuxi may possess hypotensive, antiplatelet aggregation, analgesic, anti- inflammatory and antitumor effects. The origin of Niuxi is Achyranthes bidentata (Amaranthaceae). However, people mistake the root of Strobilanthes forrestii (Acanthaceae) for the root of Cyathula officinalis (Amaranthaceae) in Taiwan. Therefore, we compared the above mentioned pharmacological effects of the methanol extracts of the three commercially available Niuxi species. The results showed that all three species exhibited analgesic and anti- inflammatory effects. NX-1 showed strongest effect followed by NX-2 and NX-3 showed least effect. Only NX-l showed hypotensive effect, whilst NX-2 and NX-3 did not. NX-2 inhibited the platelet aggregation induced by arachidonic acid and collagen. Our results showed that NX-3 exhibited least biological activity among the three, and should not be used to substitute either Achyranthis Radix or Cyathulae Radix.