We studied the effects of 17 kinds of Kampo-formulations prescribed for the treatment of peptic ulcer on H,K-ATPase activity. The activity was strongly inhibited by San-o-shashin-to ([symbol: see text], IC50 = 82 micrograms/ml), Bukuryo-in ([symbol: see text], IC50 = 110 micrograms/ml), Shakuyaku-kanzo-to ([symbol: see text], IC50 = 170 micrograms/ml), Hange-koboku-to ([symbol: see text], IC50 = 290 micrograms/ml), Dai-saiko-to ([symbol: see text], IC50 = 340 micrograms/ml), Irei-san ([symbol: see text], IC50 = 380 micrograms/ml) than other Kampo-formulations. Among the 17 kinds of crude drugs contained in these Kampo-formulation, Rhei Rhizoma, Coptidis Rhizoma, Glycyrrhiza Radix, Cinnamomi Cortex, and Poria have notable inhibitory effects (IC50 = 19-57 micrograms/ml). H,K-ATPase activity was inhibited by sennoside A (Rhei Rhizoma), sennoside B (Rhei Rhizoma), ergosterol (Poria), coptisine (Coptidis Rhizoma), glycyrrhizin (Glycyrrhiza Radix), glycyrrhetic acid (Glycyrrhiza Radix), gallic acid (Cinnamomi Cortex) in the 21 components of these crude drugs (IC50 = 1.6-7.9 x 10(-4) M). The inhibition of San-o-shashin-to and Bukuryo-in is considered to be mainly attributed to Rhei Rhizoma and Poria, respectively. The anti-gastric ulcer effects of San-o-shashin-to and Bukuryo-in may be ascribed to the inhibition of H,K-ATPase activity.