A bromhexine ion-selective PVC membrane electrode based on bromhexinium tetraphenylborate has been prepared with dioctyl phthalate as plasticizer. The electrode showed a linear response with a slope factor of 57.5 mV/concentration decade at 20°C over the concentration range from 4 x 10 -4 to 10 -1 M bromhexine. The effects of membrane composition, pH of the test solution, and the time of soaking on the electrode performance were studied. The electrode exhibited good selectivity for bromhexine with respect to a large number of inorganic cations and organic substances of biological importance. The standard addition method and potentiometric titrations were used to determine bromhexine concentrations in pure solutions and in a pharmaceutical preparation, with satisfactory results.