Conventional polymerized polyaniline (PANT) dissolved in dimethyl sulphoxide (DMSO) was used as 'seed' to induce the polymerization of aniline and hence prepare PANT nanofibers. The different preparation conditions including acid concentration, reaction time, aniline concentration, PANI/DMSO amount, PANI/DMSO concentration, acid and organic solvent kinds were investigated to discuss the influence of these conditions on the morphology and conductivity of the resulting samples. FF-IR spectra were measured to give further proof for the different effect on the conductivity. The scanning electro microscope images of PANT product extracted from the reaction solution at different time were collected and a comparison between this 'seeding' polymerization, conventional and rapidly mixing polymerization was also made to make clear the advantage of this approach and the mechanism of the formation of PANT nanofibers. (c) 2006 Elsevier Ltd. All rights reserved.