A high-performance liquid chromatographic method for the determination of cinnamic acid in Cinnamomi ramulus and paeoniflorin in Paeoniae radix was established. The samples were separated by a LiChrospher RP-18 column with water-acetonitrile-methanolacetic acid (61:34:5:0.1 or 80:15:5:0.1, v/v) as