Abstract The photocorrosion of a strontium titanate photoanode was studied under acidic, neutral and alkaline conditions. It was found that in 0.5 M H 2SO 4, SrTiO 3 corrodes very rapidly upon band-gap irradiation with an external bias. Assuming that the photocorrosion is a two-hole process releasing strontium ions, we calculated that the corrosion corresponds to 10% of the photocurrent. In the dark or under open-circuit conditions no substantial corrosion is found. In a neutral medium the corrosion is much less, although still considerable. Chips of titanium oxide appear on the surface due to the loss of strontium. Under alkaline conditions no substantial corrosion was found.