An amperometric enzyme electrode for the detection of hypoxanthine in fish meat is described. The hypoxanthine sensor was prepared from xanthine oxidase immobilized by covalent binding with glutaraldehyde and bovine serum albumin on a nafion-coated platinum disc electrode. The responses for hypoxanthine were obtained in 0.1 mol L 1 phosphate buffer (pH 7.0), at potential of 600mV vs Ag/AgCl. This biosensor provides a linear response for hypoxanthine in the concentration range of 2.00x10 6 -1.85x10 4 mol L 1 (r=0.9989). The response time is less than 30 s for the useful response range and the lifetime of this electrode was excellent for at least ten days without loss of the response. The sensor can be applied to the determination of hypoxanthine in fish meat and it is effective for eliminating interferants from coexisting substances in the samples. Application of the biosensor technique in the field of quality control is promising due to their inherent specificity, simplicity and quick response.