The photochemical behavior of 1,1-diphenylindene and 1,1-dimethylindene has been studied. The former undergoes efficient rearrangement on direct irradiation or on acetophenone sensitization, forming 2,3-diphenylindene and 1,2-diphenylindene. In contrast, 1,1-dimethylindene gave no detectable products of methyl migration but formed dimeric cyclobutanes on sensitized and direct photolysis. The structures of the two dimers formed in the sensitized reaction were assigned from their nuclear magnetic resonance spectra. It was also demonstrated that hydrogen, like methyl, migrated inefficiently if at all in this system. This difference in migratory aptitudes is discussed in terms of orbital symmetry of the indene system.