The monoterpene diepoxides isoascaridole (III), gamma-terpinene diepoxide (V), and limonene diepoxide (VIII) were prepared from the corresponding hydrocarbons and their reactivity in photoinitiated cationic polymerization examined. Both V and VIII underwent facile and rapid polymerization to give crosslinked polyethers III, but although highly reactive, did not undergo crosslinking polymerization. With the aid of model compounds it was determined that the rearrangement of one of the epoxy groups of III takes place in the presence of photogenerated acid to give an epoxy ketone (XIII) as the primary product. XIII undergoes very sluggish polymerization.