The influence of A:B cation non-stoichiometry on the structural and electrical properties of BaCeO3 and of 15% Gd-doped BaCeO3 has been investigated. X-ray powder diffraction and water uptake measurements suggest the occupation of Ba sites by Gd in barium-deficient, doped materials. This phenomenon is exacerbated by high temperature processing, which causes additional loss of barium. The relationship between defect chemistry, stoichiometry and conductivity, as measured by a.c. impedance spectroscopy, is discussed.