Raman spectra of Yb-doped strontium cerate SrCe1-xYbxO3-delta were measured to evaluate their defect structure, which is much expected to influence their physical properties, such as solubility and diffusivity of protons in these oxides. In spectra, a signal showing existence of oxygen vacancies was observed at about 630 cm(-1) for doped samples. The intensity of this band increased with oxygen vacancy formation by Yb-doping and by annealing at high temperatures in dry [low P(H2O)] or reducing [low P(O-2)] conditions. Since a clear relationship between a peak intensity of the oxygen vacancy band and dopant concentration was obtained, it was found oxygen nonstoichiometry in SrCe1-xYbxO3-delta system could be evaluated using this relationship. (C) 2003 Elsevier B.V. All rights reserved.