Electrical conduction in substituted spinel-type oxides was studied by an electrochemical method. Many substituted samples based on MgAl2O4, ZnAl2O4, etc. showed the mixed phase, where enhanced electrical conduction was not observed. Oxide ion conduction was observed in the inverse spinel-type solid solution based on Zn,2TiO4. The maximum conductivity is 2.0 X 10(-3) S cm(-1) at 1000 degrees C for Zn1.30Ti0.65Ta0.35O4. The oxide ion conduction was considered to be due to the interstitialcy-like oxide ion migration. These results are discussed in relation to the crystal phases.