Abstract: A membrane electrode based on incorporating ephedrine tetraphenylborate in a plasticized polyvinyl chloride film was prepared and the results of application to determination of ephedrine hydrochloride injection and tablet was reported. The elctrode shows Nernstian response over the concentration range from 10^-1 M to 10^-3 M with a slope of 58.7 mV/concentration decade and the detection limit was found to be 5.7×10^-5 M. With this electrode to determine ephedrine hydrochloride injection and tablet by direct potentiometric method, satisfactory results were obtained. The coefficients of variation of ten determinations of injection and tablet were±1.2% and ±1.5% respectively and the results are in agreement with those obtained by volumetric method. No interferences is caused by excipients. The present method is more rapid and simpler than the volumetric method.