Products formed by rearrangement of epoxide compounds provide useful intermediates in organic syntheses and some of them are valuable as raw materials in the chemical industry. Many studies on the catalytic rearrangement of the epoxides have been made. The reactions which have been used most frequently are homogeneous with acid or base catalysts such as BF3, MgBr2, t-BuOK, or lithium dialkylamides; the acid catalysts form mainly carbonyl compounds (ketone and aldehyde) and the base catalysts in most cases yield allylic alcohols. Recently the heterogeneous reaction over solid catalysts was also investigated, but the catalysts used were just alumina and silica gel, solid acid and base catalysts, and it is very recent that various kinds of the solid acids and bases have been used as catalysts for epoxide isomerization, especially by the authors (Section VI-A). Studies with molten salts are few, and investigations with metal complex and organometal catalysts have just begun.