A novel H(2)O(2) biosensor is described which is based on immobilization of horseradish peroxidase (HRP) on DNA/electrodeposited, ZrO(2)/modified, gold electrode. The DNA is attached via its 5' end to ZrO(2) 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 H(2)O(2) linearly between 3.5 microM and 10 mM with a detection limit of 0.8 microM 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.