The influence of yttrium doping on the ionic and electronic conductivities of α alumina developed on a β NiAl alloy by oxidation at 1100[ddot]C was investigated by electrochemical measurements, in order to point out the possible effect of this element on the transport properties of alumina scales. It appears that the yttrium influence is small. It slightly reduces the ionic transport number at low oxygen pressure and increases it at high pO2: the alumina scale behaves as an ionic conductor near the substrate-oxide interface and progressively becomes a mixed conductor or an electronic conductor near the outer oxide-gas interface. The ionic-electronic transition is sharper for undoped