An alternative route for synthesis of poly(ethylene terephthalate)-poly(aniline) composite and its use for peroxidase immobilisation is presented. The composite was synthesized by submitting polyethylene terephthalate (PET) plates to hydrazinolysis treatment, followed by polyaniline (PANI) synthesis over the PET surface. The composite was characterized by photomicrography and multiple reflectance infrared spectrometry. HRP immobilisation was very efficient, presenting 40% enzyme activity retention in the following conditions: immobilisation time of 90 min, at 4degreesC, pH 4.5 and enzyme concentration of 0.01 mg ml(-1). The optimum reaction pH was 7.0 and the enzyme continued to recognize its substrates after the immobilisation process. A slight difference between K-m and K-m.app values was observed. The immobilised HRP showed higher storage stability than free enzyme. The system PET-PANIG-HRP also showed high operational stability, maintaining 70% activity after 60 days of reutilization and storage. (C) 2003 Elsevier Ltd. All rights reserved.