Benzoyl peroxide was used as a novel oxidizing agent in the preparation of a polyaniline (PANI) dispersion. Aniline was oxidized by benzoyl peroxide into a PANI dispersion in the presence of poly(vinyl pyrrolidone) (PVP) as a stabilizer. A pure PANI dispersion in water was prepared by the dispersion of the isolated wet and dry forms of PANI powder. The size of the PANI particles in the water medium was measured for the reaction mixture and wet and dry composites with a particle size analyzer and a zeta sizer. The hydrodynamic diameter of the PANI particles ranged from 435 to 970 nm. The size of the PANI particles was found to be lower in the wet composite. PANI particles with a lower volume mean diameter (140 nm) and narrow size distribution (100-190 nm) were observed in the PANI-PVP wet composite. The PANI dispersion was characterized with Fourier transform infrared, ultraviolet-visible, differential scanning calorimetry, and scanning electron microscopy measurements. (c) 2008 Wiley Periodicals, Inc.