The salient and peculiar features of the oxidation of dicyclopentene and unsaturated alicyclic hydrocarbons with a medium-sized carbon ring into the corresponding epoxides have been studied. Organic hydroperoxides, aqueous hydrogen peroxide, and peracids have been used as oxidizing agents. The reactivity of the substrates in each of the oxidation processes under consideration has been estimated, and conditions providing a high epoxide yield have been chosen. The advantages and disadvantages of each process taking into account the problems of isolation of the desired product are considered. The results obtained allow the peracid method to be recommended for the synthesis of dicyclopentene epoxide as an effective and convenient for practical implementation.