Ionic conductivity of perovskite-type oxides is discussed in terms of structurally related parameters. Electrical conductivity data of perovskite-type oxides, reported as oxygen ion conductors, were collected from literatures and the correlation between the electrical conductivity of these compounds and the structurally related parameters, such as tolerance factor, specific free volume and oxygen deficiency was examined. The tolerance factor and the specific free volume were both a function of ionic radius and the tolerance factor decreased with increasing the specific free volume. The optimum tolerance factor was found to be around 0.96 due to the balance between the specific free volume and the tolerance factor in order to obtain the maximum electrical conductivity for A(III)B(III)O(3)-type perovskites. The optimum oxygen deficiency to obtain the maximum electrical conductivity was around 0.2, The effect of ionic size of dopant ions in A and B site on electrical conductivity was also discussed.