A novel strategy for discovering biologically active components in traditional Chinese herb remedies was performed from a pharmacokinetic view. The hypothesis was that the active compounds should appear in blood and urine with appropriate blood concentrations and urinary excretion rates after the administration of herbal-extract mixtures. In this research, we applied our procedures to Saiboku-To, one of the most popular Chinese herbal medicines in Japan. Consisting of 10 different plant extracts, it is used for the treatment of bronchial asthma. The analytical method adopted was a rapid-flow fractionation (RFF) for extraction-fractionation of lipophilic components in urine followed by silica-gel high-performance liquid chromatography (HPLC) equipped with a multichannel ultraviolet (uv) absorption detector. beta-D-Glucuronidase-treated urine samples collected before and after the administration of Saiboku-To to healthy and asthmatic subjects were treated with the RFF apparatus to afford three pH-dependent fractions: strongly acidic (S), weakly acidic (W), and neutral (N). HPLC of these fractions, monitored by the multichannel uv detector, showed three new peaks in the postadministrative urine: one in the N fraction, two in the W fraction, and none in the S fraction. A compound in the N fraction was identified with authentic magnolol, a major component in Magnolia officinalis. Two compounds in the W fraction were identified by comparison with authentic samples as 8,9-dihydroxydihydromagnolol and liquiritigenin, metabolites previously isolated from M. officinalis and Glycyrrhiza glabra, respectively.