We report a synthesis of polyaniline (PANI) suspension of particles with size of about 2-3 nm. This nano-colloid was obtained by aniline oxidative polymerization in dilute and semi-dilute solutions of sodium poly(styrene sulfonate) (PSSNa) with molecular weight equal to 6800 g/mol or higher. The ionic strength of the solution was about 1 x 10(-2) mol/l, which corresponds to aniline (and, respectively, PANI) concentration lower than 4.6 x 10(-2) mol/l in 5 M solution of formic acid. To the best of our knowledge, it is the first communication dealing with preparation of particles with a molecular scale dimensions, using a rigid backbone polymer with a very strong intermolecular interactions. Important modification of the electronic properties of such dispersed PANI, compared to those of the well-known bulk PANI, was observed. (C) 2004 Elsevier Ltd. All rights reserved.