Polyaniline salts are prepared by doping of polyaniline base with different Bronsted acids (H2SO4, HCl, HClO4, and HBF4) and organic acid [5-sulfosalicylic acid (SSA), p-toluene sulfonic acid (PTSA)]. Polyaniline complexes are also prepared by using Lewis acids (ZnI2 and FeCl3). Polyaniline salts and polyaniline complexes are characterized by physical, electrical and spectral methods. Polyaniline salts and polyaniline complexes are used as catalyst for the Mannich-type reaction under solvent free condition. p-Amino carbonyl compounds obtained in high yields with simple and more environmental benign procedure. The use of polyaniline catalysts are feasible because of their easy preparation, easy handling, stability, easy recovery, reusability, good activity and eco-friendly. (C) 2004 Elsevier B.V. All rights reserved.