A nanocomposite was prepd. from chitosan and zirconium oxide nanoparticles (nano-ZrO2) and then electrophoretically deposited on an indium tin oxide (ITO) coated glass substrate. Morphol. investigations reveal a uniform wrapping of nano-ZrO2 in chitosan, with a particle size of ∼20 nm. The enzymes lipase and glycerol dehydrogenase were immobilized on this electrode to obtain an amperometric biosensor for the lipid tributyrin. Lipase hydrolyzes tributyrin to form glycerol which is oxidized by glycerol dehydrogenase under the formation of reduced NAD (NADH). The electrochem. response of the NADH formed was studied via cyclic voltammetry using hexacyanoferrate as a mediator. The current measured (best at a working voltage of 0.35 V vs. Ag/AgCl) is related to the concn. of tributyrin in the 0.25 to 4 mg mL-1 range. The lower limit of detection is 155 μg mL-1, and the response time is 45 s. The sensor is fairly stable in that its activity is reduced to 85% within a period of 11 wk. This bioelectrode has been applied to the detn. of triglycerides in serum samples. [Figure not available: see fulltext.].