Poly(vinylferrocenium) perchlorate-polyaniline (PVF+-PANI) composite film was synthesized electrochemically on Pt electrode in a methylene chloride solution containing a mixture of poly(vinylferrocene) (PVF) polymer and aniline monomer. PVF+ polymer in the composite film was used as an electron transfer mediator. The composite coating showed significant electrochemical activity towards hydroquinone (HQ) at pH 4, with high sensitivity and a wide linearity range. The interaction of HQ with PVF+ and PANI homopolymer films was investigated electrochemically and spectroscopically. HQ molecules are accumulated on the electrode surface due to trapping by both polymers in the composite film and then oxidized catalytically by PANI. The most significant contribution of PVF+ polymer is that it facilitates electron transfer in the composite film. The linear response range was found to be between 1.60 x 10(-4) mM and 115 mM (R (2) = 0.999) at 0.45 V vs saturated calomel electrode. The limit of detection (LOD) was 4.94 x 10(-5) mM.