The ionic and n-type conductivities of ceria-based electrolytes doped with gadolinium (10 and 20 cation %) or gadolinium and praseodymium (2% Pr and 18% Gd) were studied by impedance spectroscopy in air, between 573 and 1273 K, and by constant frequency (10 kHz) conductivity measurements as a function of the oxygen partial pressure (p(o2)) between about 10(-20) atm and air in the temperature range 1073 to 1273 K. Ion blocking measurements were also performed between 1073 and 1273 K with air at the reversible electrode. From data obtained with different experimental techniques it was concluded that estimates for the electronic conductivity of all compositions were consistent and that all materials behaved in a rather similar manner. Estimated n-type conductivities suggest that Pr-doped materials have a slightly lower electronic conductivity and a larger electrolytic (and ionic) domain, but overall differences are quite small. The model behavior used in analyzing experimental results is discussed based on the existing knowledge of the defect chemistry of ceria-based electrolytes, and a range of working conditions is identified where the ionic conductivity can be assumed constant and the electronic conductivity proportional to p(o2)(-1/4).