The Keggin-type di-vanadium-substituted silicotungstate [gamma-1,2-H2SiV2W10O40](4-) with the {VO-(mu-OH)(2)-VO} core catalyzes the epoxidation of various alkenes using only 1 equiv. H2O2 with the high epoxide yield and high efficiency of H,02 utilization under very mild reaction conditions. Notably, this system shows unique stereospecificity, diastereoselectivity, and regioselectivity, which are quite different from those reported for the epoxidation systems including [gamma-SiW10O34(H2O)(2)](4-). (c) 2006 Elsevier B.V. All rights reserved.