The title reactions occur readily. With acetonitrile chosen as the solvent, 17 of them were studied by kinetic methods. As is true for other MTO-catalyzed reactions, peroxorhenium complexes are the active species. Under the conditions of hydrogen peroxide present in large excess, usually employed here, CH3Re(O)(eta(2)-O-2)(2)(OH2) was the major reactive catalyst present : The rate constant between it and the dienes increase or decrease as substituents add or remove electron density from the C=C bonds, suggesting a concerted mechanism in which the double bond attacks a peroxide oxygen. Many of the products are diols; some rearranged, except when the stability of carbocation intermediates for epoxide ring opening are so unstable as to prolong their lives. When urea-hydrogen peroxide was used instead, the monoepoxides were obtained.