Polyoxometalates (abbreviated as POMs) are useful acids and oxidation catalysts in various reactions since its catalytic features can be controlled at a molecular level. This review summarizes some recent research progress in catalytic application of Keggin and Wells-Dawson type polyoxometalates. Particular attention is given to most developments of our recent studies on the use of POMs as heterogeneous and homogeneous catalysts for the selective oxidation and acid-catalyzed reactions. (c) 2006 Elsevier B.V. All rights reserved.