Polyaniline (PANI), a conducting polymer, was prepared by the oxidation of aniline with ammonium peroxydisulfate in various aqueous media. When the polymerization was carried out in the solution of strong (sulfuric) acid, a granular morphology of PANI was obtained. In the solutions of weak (acetic or succinic) acids or in water, PANI nanotubes were produced. The oxidation of aniline under alkaline conditions yielded aniline oligomers. Fourier transform infrared (FTIR) spectra of the oxidation products differ. A group of participants from 11 institutions in different countries recorded the FTIR spectra of PANI bases prepared from the samples obtained in the solutions of strong and weak acids and in alkaline medium within the framework of an IUPAC project. The aim of the project was to identify the differences in molecular structure of PANI and aniline oligomers and to relate them to supramolecular morphology, viz. the nanotube formation. The assignment of FTIR bands of aniline oxidation products is reported.