Composite colloidal particles of polypyrrole-poly(vinyl alcohol) and polypyrrole-poly(vinylpyrrolidone) doped with benzenesulfonate were prepared by using poly(vinyl alcohol) and poly(vinylpyrrolidone) as steric stabilizers. Voltammetric investigation indicated that the particles possessed virtually no redox activity, probably due to insulation effects of the stabilizer layer adsorbed on the polypyrrole nucleus or due to the formation of reduced polymer at the nucleus surface. To make the colloidal particles electroactive, a polypyrrole-poly(vinyl alcohol) composite doped with 9,10-anthraquinone-2-sulfonate was prepared. The colloid was characterized by thermogravimetry coupled with mass spectroscopy and by Fourier transform infrared (carbonyl vibration frequency) to confirm that the anthraquinone was inserted in the polypyrrole matrix. The inserted quinone exhibited electroactivity and was nor ejected appreciably on anion exchange and redox reaction. Quinone mediation was also studied by adding the quinone into a dispersion of polypyrrole-poly(vinylpyrrolidone) doped with benzenesulfonate, but the two quinone systems displayed different voltammetric behavior. Investigation on electron spin resonance is also discussed to characterize the pH dependence and redox activity of the colloidal dispersions.