THERE is at present great interest in high energy density batteries, especially for use in urban transport1. For this application an electrically rechargeable system would be ideal, and night charging would assist in levelling out the demand for electricity. Metal-air batteries (notably zinc-air) are probably nearest to practical usefulness, but one limitation to their large scale use is the fact that a noble metal catalyst (usually platinum) may need to be used in the air electrodes, which have to reduce oxygen from the air to OH− ions in the concentrated alkali electrolyte and subsequently to act in reverse for recharging. I report here preliminary tests in which lanthanum cobaltite—a semiconducting oxide—has given results comparable to those produced by platinum. The material clearly deserves detailed further attention and, after discussion of the results, suggestions are made for its development into a practical electrode.