We report the successful measurement of the specific surface area of chemically synthesized and treated polyaniline (PANI) and its composite PANI/silica (SiO2). PANI was synthesized chemically from an aqueous solution of aniline and hydrochloric acid (HCl) in the presence of an oxidant, ammonium peroxydisulfate [(NH4)(2)S2O8]. In the synthesis of PANI/SiO2, SiO2 was incorporated from its colloidal solution contained in the solution for the polymerization of PANI. PANI and PANI/SiO2 thus synthesized were pretreated with double-distilled water (pH = 6.95), aqueous HCl (pH = 1.09), and aqueous ammonia (pH = 10.15) solutions to control their pH levels. Surface morphologies of the treated PANI and PANI/SiO2 matrices were investigated with scanning electron microscopy. The successful incorporation of SiO2 into the PANI/SiO2 composite was confirmed by the characteristic infrared absorption band at 1096 cm(-1). The adsorption of methylene blue, which was found to follow the Langmuir isotherm, onto the prepared materials was probed to estimate the real surface area. The base-treated PANI matrix showed a higher surface area than the acidic and neutral ones. The incorporation of SiO2 into the PANI matrix yielded a larger surface area. However, the treated PANI/SiO2 showed the same trend as the treated PANI matrices. (C) 2008 Wiley Periodicals, Inc.