SR VUV photoemission is used to explore the surface reactivity of La1-xSrxCo1-yCuyO3 and La2-xSrxCo1-yCuyO4 in aqueous solution. This is combined with studies of activity in peroxide decomposition in order to assess the usefulness of the materials as aqueous oxidation catalysts. Both surface reactivity to water, and activity in peroxide decomposition decrease with increasing Cu content, suggesting that the Cu-rich A2BO4 layered perovskites are more suitable potential catalyst materials than the Co-rich ABO3 perovskites. Changes in reactivity are discussed in terms of the transition metal d electron count. © 1999 Elsevier Science B.V. All rights reserved.