The superconducting compound YBa2Cu3O7and the insulating material La2CuO4have been examined using liquid-metal ion-induced secondary-ion mass spectrometry. The results revealed surface reactions with moisture as well as some contamination by hydrocarbons. These surface layers were readily sputtered away, but the apparent presence of yttrium, barium and lanthanum hydroxides could play a significant part in their surface conduction characteristics. The relative intensity of the sputtered ion MO+was found to be a logarithmic function of its dissociation energy.