The incorporation of protons into two perovskite oxides has been investigated using Secondary Ion Mass Spectrometry (SIMS). The SIMS analysis was carried out on an Atomika 6500 instrument using Cs+ primary bombardment and negative secondary ions. Samples of SrCe0.95Yb0.05O3-delta were subjected to anneals in either wet or dry oxygen at 600 degrees C prior to analysis. Proton incorporation into La0.5Sr0.5CoO3-delta was briefly investigated. Difficulties associated with the determination of the hydrogen concentration in oxides using SIMS are discussed, with special reference to problem of mass interferences, the use of isotopes (D-2) and the interpretation of negative ion SIMS.