Nanoparticles of electroconductive polymers were prepared in micellar solution as a polymerization medium to overcome the poor processability of electroconductive polymers. The morphologies of particles were studied through SEM and electrical conductivities of pellets formed with nanoparticles were measured by four-probe apparatus. Among many other electroconductive polymers, nanoparticles of polyaniline and poly(3,4-ethylenedioxythiophene) were prepared in anionic sodium dodecyl sulfate and dodecylbensen sulfonic acid micellar solutions. The sizes and shapes of particles were similar to those of micelles. The electrical conductivities of pellets formed with nanoparticles were 20 and 50 S/cm depending upon the polymerization conditions, which are higher values than those of pellets formed with particles prepared in bulk solutions. (C) 2002 Elsevier Science B.V. All rights reserved.