The chemical oxidation of aniline to form polyaniline (PANI) films and powder samples was made using Fenton reagent as an oxidizing agent in aqueous sulfuric acid medium. The PANI films were monitored by using the quartz crystal microbalance and the electronic absorption techniques. The optimum concentration was determined and the results were justified by measuring the UV-vis absorption spectra for the in situ PANI films. The conductivity for the PANI films and powder samples, prepared in different conditions, was measured. Also, the IR spectra, X-ray and the thermogravimetric analysis for the PANI powder formed in the bulk were measured and compared with the polymer prepared using ammonium peroxydisulfate. A preliminary investigation to the dielectric properties of the polymer powder was measured and discussed. (C) 2008 Wiley Periodicals, Inc. I Appl Polym Sci 110: 3410-3419, 2008