A new route to insert polypyrrole (PPy) into arachidic acid (C 20 A) multilayers is investigated. It consists of three steps of reactions: (i) C 20 A films are first converted to silver arachidate (C 20 Ag) films; (ii) exposing C 20 Ag films to perchloric acid (HClO 4 ) gas leads to recovery of C 20 A films that contain AgClO 4 ; (iii) finally, pyrrole molecules, introduced by vapor diffusion into the films, are polymerized under action of intercalated AgClO 4 to form oxidized PPy. The insertion reactions and film structure throughout PPy manipulation are characterized by means of Fourier transform infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy