Ultrafine fibers of polyaniline doped with camphorsulfonic acid (PAn.HCSA) blended with polyethylene oxide (PEO) were prepared by a non-mechanical, electrostatic spinning ("electrospinning") technique. The morphology and fiber diameter of electrospun polyaniline blend fibers revealed that both the PEO and the PAn.HCSA/PEO blend fibers had a diameter ranging between 950 nm and 2.1 mu m, with a generally uniform thickness along the fiber. The UV-visible spectra of these electrospun fibers were similar to those for cast films produced from the same solutions. As expected, the conductivity of the non-woven fiber mat, as measured by the four-point probe method, was slightly lower than that of a cast film, due to the high porosity of the non-woven mat. The rate for the vapor phase de-doping/re-doping of the electrospun fibers is at least one order of magnitude faster than for cast films, stressing the enormous effect an increase in the surface-to-volume ratio, accomplished by electrospinning the material into fibers, can have on the selected chemical properties of polyaniline blends. (C) 2000 Elsevier Science S.A. All rights reserved.