Palladium-palladium oxide film formed by the RF reactive sputtering technique was used for pH measurement. The potentiometric mode of operation was employed and an Ag/AgCl electrode was used as the reference electrode. The Pd-PdO film was formed on both alumina and polycrystalline silicon, and sputtering conditions to produce Pd-PdO film with good pH response characteristics were empirically defined. The Pd-PdO showed good pH response, ~ 54 mV/[pH] at 25°C over the pH range of 3–9. The temperature dependency and dissolved oxygen effect on the film when used as a pH sensor were investigated and discussed. Copyright © 1986 by The Institute of Electrical and Electronics Engineers, Inc.