This work reports a simple and effective method to prepare polyaniline (PANI) nanotubes with rectangular or circular cross section and hollow microspheres by using basic amino acids L-lysine or L-arginine as dopants and pH buffer agents, respectively. The research reveals that the pH value of the reaction solution at the beginning stage is a crucial factor to form PANI microstructures. The L-lysine and L-arginine have isoelectric point 9.74 and 10.76, which can maintain reaction solution at high pH value at the beginning reaction and assist aniline to couple in ortho-position forming phenazine unit in the oligomer chain. The oligomer produces rectangular nanorods or microspheres by interaction. These oligomer microstructures act as templates for further polymerization to form PANI rectangular nanotubes and hollow microspheres. Decreasing the concentration of the basic amino acid or using acidic amino acid, the round nanotubes are formed. This method provides a simple route to prepare PANI microstructures with different morphologies without any foreign template or surfactant, and raises a new view on the polymerization process. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 2173-2182, 2011