The Keggin-type iron-substituted polyoxometalates have been used as catalysts for the oxygenation of alkanes in homogeneous reaction media using hydrogen peroxide as an oxygen donor. The efficiency and activity for the utilization of hydrogen peroxide greatly depended on the iron centers and diiron-substituted [gamma-SiW10{Fe(OH2)}(2)O-38](6-) showed the highest efficiency of hydrogen peroxide utilization and conversion. Such a structure dependency of the catalysis is significant, and the remarkable catalytic performance of diiron-substituted polyoxometalate may be related to the catalysis by methane monooxygenase. It is remarkable that the efficiency of hydrogen peroxide utilization to oxygenated products reached up to ca. 100% for the oxygenation of cyclohexane catalyzed by diiron-substituted [gamma-SiW10{Fe(OH2)}2O(38)](6-) polyoxometalate. Not only cyclohexane but also n-hexane, n-pentane, and adamantane were catalytically oxygenated with high efficiency of hydrogen peroxide utilization. It was also suggested that diiron-substituted polyoxometalate was stable under the conditions used and in the presence of hydrogen peroxide.