Glucose oxidase (GOD) has been immobilized in Layer-by-Layer (LbL) films, adsorbed alternately with poly(allylamine) hydrochloride (PAH) layers, onto an ITO substrate modified with a Prussian Blue (PB) layer. The ITO/PB/GOD-PAH heterostructures were tested in amperometric glucose biosensors, with a high sensitivity of 16 microA mmol(-1)lcm(-2) and a limit of detection of 0.20 mmoll(-1) being achieved. This high sensitivity is attributed to the ultrathin nature of the film in addition to the low operating potentials that could be used due to the efficient catalysis of H(2)O(2) produced in the enzymatic reaction in the presence of Prussian Blue. The biosensors are highly selective to glucose, as demonstrated by the lack of interference from possible interferents such as ascorbic and uric acids and acetominophen. The stability of the biosensors was checked by observing an almost constant sensitivity for a period of approximately 20 days, thus indicating a stable adsorption of GOD.