A wet chemical route has been used to synthesize the oxygen deficient perovskite BaZr0.5Yb0.5O3-delta. Analysis of X-ray powder diffraction data showed that both dried and hydrated samples adopt cubic crystal structures of space group Pm (3) over barm. Dynamic thermogravimetric analysis showed a significant mass loss for the hydrated sample compared to the dried sample, indicating that similar to 28% of the oxygen vacancies are filled by protonic defects. The strong O-H stretch band, 2500-3500 cm(-1), in the IR absorbance spectrum also clearly manifests the presence of significant levels of protons in the hydrated material. Proton conductivity was investigated on prehydrated (under dry Ar) and as-prepared (under wet Ar) samples. The heating cycle of the prehydrated sample showed higher proton conductivity compared to the cooling cycle, especially in the intermediate temperature range (150-550 degrees C). Finally, comparison with data for BaZr0.9Yb0.1O3-delta revealed that the more heavily doped sample showed higher proton conductivity compared to the more lightly doped sample. (C) 2008 The Electrochemical Society.