The use of new "tailor-made" reactive statistical copolymers for the synthesis of sterically stabilized polypyrrole colloids is described. These copolymer stabilizers are readily prepared by free-radical copolymerization of (bi)thiophene-based vinylic monomers with various hydrophilic vinyl monomers such as 2-(dimethylamino)ethyl methacrylate, 2-vinylpyridine, N-vinylpyrrolidone or oligo(ethylene oxide) methacrylate. Monitoring the oxidation of the bithiophene graft sites using visible absorption spectroscopy provided evidence for stabilizer grafting. Relatively high stabilizer efficiencies were obtained and the resulting spherical polypyrrole particles contained 14 to 48% stabilizer by mass and had reasonably narrow size distributions in the 50-100 nm range. Pressed pellet conductivities were as high as 4 S cm(-1). X-ray photoelectron spectroscopy studies indicated that the polypyrrole particles were coated with an overlayer of grafted stabilizer, as expected from steric stabilization theory. This route to polypyrrole particles is believed to be completely general and is expected to allow the rational design of steric stabilizers containing a wide range of functional comonomers. This should be useful for the improved design and performance of immunodiagnostic assays based on polypyrrole "marker" particles.