The potential-pH relations of aluminum wire electrodes were studied in 0.1M potassium chloride and in buffer solutions. Linear pH responses with a slope about -90 mV per pH unit over a pH range of 3 to 14 were obtained. Pretreating the electrodes in alkaline solutions of pH greater-than-or-equal-to 10.6 for several minutes was an essential first step in order to elicit the pH responses.The results are explained with the consideration of the hydration of the aluminum oxide and the formation of aluminum hydrides. The diameter of wires used and the ionic strength of the bathing solutions studied had little effect on the pH responses. The effects of some complexing agents commonly used in buffers were investigated. The reproducibility and the short-term stability of the electrodes as well as the electrode lifetime were investigated. Practical potential applications and possible ways for improving of the electrode performance are suggested.