Electrodes were fabricated to be selective for Levobetaxolol. The coated-wire approach of Freiser et al. was used, but the polymeric materials were very similar to those used by the Salford group to construct membrane electrodes, less susceptible to interference, by virtue of covalent attachment of the counter-ionophore to the PVC membrane. The electrodes obtained combined the advantages of quick response and greater selectivity. A commercially available carboxylated poly(vinyl chloride) polymer behaved nearly identically to the end-sulfated polymer used by the Salford group.