MeReO(3) was synthesized by conversion of AgReO(4), and used as catalyst for epoxidation of cyclohexene and 1,5-cyclooctadiene with urea-H(2)O(2) complex in 5 com. ionic liqs. The products were sepd. from the reaction mixt. by extn. with org. solvents (Et(2)O, pentane, cyclopentane). The products contained also resp. diols formed by spontaneous opening the oxirane rings. 1-Butyl-3-methytimldazolium tetrafluoroborate was the most efficient medium of the reactions studied. The phosphonium salts used showed lower applicability as reaction mediums.