Some kinds of sugar and amino acid are used to interact with polyaniline emeraldine base in neutral aqueous solution. PANI complexed with these molecules shows interesting induced circular dichirom (ICD) spectra, which indicates that excess one-handed helical structure is induced on PANI. Furthermore, opposite ICD spectra are observed for PANI while it is interacted with L- and D-amino acid, respectively. It is presumed that H-bonding interaction plays a central role in such a helical induction. This is the first example to prepare optically active PANI in neutral solution by one step without protonating EB into polycation in advance. (C) 2003 Elsevier Ltd. All rights reserved.