The potentials of electropolymerization of aniline on a Pt anode surface in aqueous 0.5 mol dm-3 H2SO4 + 0.1 mol dm-3 C6H5NH2 solution have been investigated. By means of simultaneous cyclic voltammetry and in situ Raman spectroscopical measurements the constitutent units and structure were proposed for the polymer chain in the electrodeposited film. Possible transitions between constituent units and structural change during exposure of the deposited polymer film to air have been discussed on the basis of Raman spectra.