A novel H2O2 biosensor is described which is based on immobilization of horseradish peroxidase (HRP) on DNA/electrodeposited, ZrO2/modified, gold electrode. The DNA is attached via its 5' end to ZrO2 and this provides a microenvironment for the immobilization of various biomolecules and promotes electron transfer between HRP and the electrode surface. Under optimized conditions, the biosensor reduced H2O2 linearly between 3.5 mu M and 10 mM with a detection limit of 0.8 mu M at a signal-to-noise ratio of 3. In addition, the developed biosensor shows an acceptable stability and repeatability. Importantly, the analytical methodology could be further developed for the immobilization of other proteins and biocompounds.