The solid solution range and oxygen ion conductivity of Sr/Ca and Mg doped NdGaO3 were investigated. In the formula Nd(1-x)M(x)Ga(1-y)Mg(y)O(3-delta) (M = Sr, Ca), the limit of solid solution for the A sublattice is x = 0.1, while the limit for the B sublattice is y = 0.15. The conductivity increases and activation energy decreases when only A sites or only B sites are doped. However, the conductivity decreases when both A and B sites are doped, relative to single doping only. The optimum composition at x = 0 and y = 0.1, i.e., NdGa0.9Mg0.1O2.95 has a corresponding maximum conductivity of 0.035 S cm(-1) at 800 degrees C. The conductivity shows little change over oxygen pressures ranging from 1 to about 10(-20) atm at temperatures studied, indicating that the conductivity of these compositions is essentially ionic.