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The electronic transport properties of the ordered double perovskite oxides Sr2FexMo2-xO6 (0.8 less than or equal to x less than or equal to 1.5) have been investigated. In this system, the samples (x greater than or equal to 1.2) are semiconducting in the temperature range of 4.2 less than or equal to T less than or equal to 300 K. A metal-semiconductor transition occurs when x < 1.2 and the transition temperature T-MS decreases obviously as the Fe, content decreases. Rietveld refinement of the X-ray powder. diffraction profiles indicates that the crystal structure of the compounds Sr2FexMo2-xO6 changes from a tetragonal I4/mmm lattice to a cubic Fm (3) over barm lattice around x = 1.2. (C) 2003 Elsevier Science B.V. All rights reserved.