Herba Asari (Xixin, Manchurian Wildginger, Asarum spp.) is a traditional Chinese medicinal herb commonly used as a crude drug and an ingredient in patent medicines. The herb contains aristolochic acid I (AA-I), which has recently caused several incidents of poisoning in Hong Kong. Therefore, the safe use of Asarum is questionable. The present study was undertaken to assess the levels of AA-I using liquid chromatography-mass spectrometry (LC/MS) indifferent medicinal parts of Herba Asari and some proprietary Chinese medicines (PCM) containing it as an ingredient. The AA-I content in the aerial and root portions were compared, in the form of water and methanolic extracts. The results showed that all the aerial portions of Herba Asari generally contain higher levels of AA-I than the roots (in water extract: 0.0870.06 microg/g of root and 0.3270.021 microg/g of aerial), and the methanolic extracts typically contained more AA-I than the water extracts. Moreover, all the three PCM studies showed negligible amounts of AA-I(containing 0.0370.006 microg/g). Therefore, the root portion of Herba Asari was recommended for prescription as a decoction instead of grinding it into powder for oral administration.