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 (C20Ag) films; (ii) exposing C20Ag films to perchloric acid (HClO4) gas leads to recovery of C(20)A films that contain AgClO4; (iii) finally, pyrrole molecules, introduced by vapor diffusion into the films, are polymerized under action of intercalated AgClO4 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.