Transparent conducting thin films of Al-doped and Ga-doped Zn1-xMgxO with arbitrary Mg content x were deposited on glass substrates by simultaneous RF-magnetron sputtering of doped ZnO and MgO targets, and their fundamental properties were characterized. MgO phase separation in Zn1-xMgxO films was not detected by X-ray diffraction. The Zn1-xMgxO films show high optical transparency in the visible region. Although the carrier density of the Zn1-xMgxO films decreased with increasing x, the Zn1-xMgxO films showed good electrical conductivity; electrical resistivity as low as 8 x 10(-4) Omega . cm was achieved for the Zn0.9Mg0.1O:Ga thin film. (C) 2009 Published by Elsevier B.V.