Gallotannins in six crude drugs (Galla Chinensis, Galla Halepensis, Paeoniae Radix, Moutan Cortex, Uvae Ursi Folium and Trapae Fructus) were isolated by a combination of Sephadex LH-20 column chromatography and high performance liquid chromatography(HPLC). The structures of gallotannins were determined mainly by ^1H-and ^<13>C-NMR spectroscopy as shown in Fig. 5. The gallotannins in Galla Chinensis, Paeoniae Radix and Moutan Cortex have a 1,2,3,4,6-pentagalloylglucose(6) core and those of Galla Halepensis have a 1,2,3,6-tetragalloylglucose(5) core. The depside galloyl group of hexagalloylglcuose in Paeoniae Radix and Moutan Cortex is attached to C-6 position of glucose, but that of Galla Chinensis is randomly distributed among C-2, C-3 and C-4 positions. The ^<13>C-NMR spectra indicated that the depside galloyl group in gallotannins is linked not only with m- but also p-hydroxyl group of another galloyl group. The presence of gallotannins in 154 crude drugs was tested by HPLC; seven crude drugs, Nupharis Rhizoma, Pylolae Herba, Rosa Multiflorae Fructus, Euclypti Folium, Guava (Psidium guajava L.) and Kayuptih (Melaleuca leucadendron), were found to contain gallotannins. The gallotannins in Paeoniae Radix decreased blood urea nitrogen concentration in rat serum in vivo. Moreover, gallotannins inhibited the growth of certain bacteria and the respiration of rat liver mitochondria in vitro.