In Cnidium officinale $M_{AKINO}$ and Platycodon grandiflorum A. $D_E;C_{ANDOLE}$, chlorogenic acid was identified by Rf values, color reactions on paper chromatograms and UV-absorption spectra of the eluate of phenolic spots. And isochlorogeni acid-like substance was also found in the former. $1-Phenylalanine-U-C^{14}$ and sodium $acetate-2-C^{14}$ werse fed to both plants and their incorporation ratio to chlorogenic acid and isochlorogenic acid-like substance was compared. Phenylalanine was better precursor for chlorogenic acid in both plants than acetate. But acetate showed higher incorporation ratio to isochlorogenic acid-like substance in Cnidium officinale than that of phenylalanine.