Abstract: The polyaniline/manganese dioxide composites (PANI/MnO₂) containing different amounts of manganese dioxide were prepared by chemical polymerisation of aniline using ammonium peroxodisulfate (APS) and MnO₂ as the oxidizing agent. The inclusion of PANI in the composite was confirmed by FTIR, UV-VIS, XRD and SEM analysis. It shows that PANI in the composite is amorphous and the crystal structure of MnO₂ is unchanged compared with the initial MnO₂. The PANI formed in the reaction is deposited preferentially on the MnO₂ particles giving a PANI/MnO₂ composite, in which the MnO₂ is coated with the PANI. The tree-coral-shaped PANI, which differed from the common grain-like PANI in the acid/water reaction system, was obtained by treating the PANI/MnO₂ composite in the static state with hydrochloride acid solution of aniline.