The invention relates to a potentiometric, ion-selective electrode for the measurement of cation concentration in a sample, which electrode is made of electrically conductive electrode material applied on an electrically insulating substrate using a thick-film technique and covered in the measurement area by an ion-sensitive membrane, preferably a liquid polymeric membrane. At least one water-soluble alkaline-earth metal salt is homogeneously dispersed in the electrode material. The water solubility of the alkaline-earth metal salt is preferably greater than 1.times.10.sup.-2 .mu./l, and lies preferably between 1.times.10.sup.-2 and 1.times.10.sup.-1 g/l.