ability of the oxetane. The limiting quantum yields in the case of 1,4-dicyanonaphthalene-photosensitized reaction of 2,2-di-p-tolyl- or 2,2-bis(p-mechoxyphenyl)-3,3,4-uimethyloxetane exceed unity. The mechanism is discussed in terms of electron transfer from oxetanes to the excited singlet state of the sensitizer as well as the regeneration process of the oxetane cation radical involving the hole transfer