The aim of this research project is to develop a triple- barrelled recessed biosensor with a combined tip diameter of 2-3u for simultaneous measurement of pO2, pH and cell potential. The pO2 barrel has gold as the cathode and the pH barrel has antimony/antimony oxide as the cathode. The third barrel will make use of standard methods. The biosensor offers a much needed research tool for understanding dynamic changes and metabolism at the cellular level. Development of the biosensor will be a significant contribution in the study of cellular physiology. The principles used here can be applied to make biosensors for clinical use. In fact, a satisfactory biosensor which measures several parameters is badly needed for clinical use.