In routine clinical care rapid results from pH determinations are often desired. This calls for continuousin vivo measurements. Today only intermittentin vitro pH analysis is routinely performed, as the existing transducers do not meet the clinical demands on dimensions, stability, stabilisation time, resolution and ruggedness. Here, some results from a basic experimental study on antimony-antimonyoxide pH electrodes are presented. The purpose of the investigation has been to gain some information on the electrode processes, which govern the electrode response, and to use this information to synthesise more stable and reproducible electrodes than those presently existing. These electrodes are intended, in an appropriate miniaturised form, forin vivo routine pH determinations on homo, e.g in a continuous acid-base balance surveillance application.