Iridium oxide electrodes formed by potential cycling in dilute acids were investigated for their use as pH sensors. It was shown that both the short- and long-term stabilities of such sensors were adequate for applications where an accuracy of ±0.2 pH is acceptable. It was also found that thicker oxide films which give responses of up to about 80 mV pH^–1 are to be preferred in order to ensure reproducible behaviour. As potentiometric probes either for direct monitoring of pH or for following typical acid-base titrations, these electrodes give comparable results to those obtained with glass electrodes. Several basic concepts relating to the practical management of potential-cycled iridium oxide electrodes are discussed.