Glucose potentiometric biosensor was prepared by immobilizing glucose oxidase on iodide-selective electrode. The hydrogen peroxide formed after the oxidation of glucose catalysed by glucose oxidase (GOD) was oxidized by sodium molybdate (SMo) at iodide electrode in the presence of dichlorometane. The glucose concentration was calculated from the decrease of iodide concentration determined by iodide-selective sensor. The sensitivity of glucose biosensor towards iodide ions and glucose was in the concentration ranges of 1.0 x 10(-1)1.0 x 10(-6) M and 1.0 x 10(-2)-1.0 x 10(-4) M, respectively. The characterization of proposed glucose biosensor and glucose assay in human serum were also investigated.