AbstractAntihepatotoxic activities of the components of a traditional Chinese prescription, Dai‐saiko‐tǒ, were examined employing complement‐mediated cytotoxicity in primary cultured mouse hepatocytes.Bupleuri RadixandScutellariae Radixwere shown to be active in this system but did not reach the levels of activity of the prescription. In combination,Bupleuri Radix‐Scutellariae Radix, Bupleuri Radix‐Zingiberis Rhizoma, Scutellariae Radix‐Pinelliae Tuber and Bupleuri Radix‐Zingiberis Rhizoma, exhibited effects comparable to the original prescription. It was therefore concluded that the antihepatotoxic activity of Dai‐saiko‐tǒ is due to the pharmacological interactions of their constituents. In addition, a difference in antihepatotoxic activity ofBupleuri RadixandAurantii Fructus Immaturuswas observed between their water extracts and 50% aqueous ethanol extracts, indicating that active principles in each extract of the prescription seemed to be different and, therefore, the method of extraction was an important factor in the clinical