Laser-induced fluorescence spectra in the 330-370 nm region are assigned to the five expected methyl substituted vinery radicals : 1-methylvinoxy, 2-methylvinoxy, 1,2-dimethylvinoxy, 2,2-dimethylvinoxy, and 1,2,2-dimethylvinoxy radicals. Substituted vinery radicals were produced by photolyses or by chlorine or fluorine atom reactions with ketones, aldehydes, or ethers. These radicals were also observed when reacting oxygen atoms with olefins such as propene, cis- and trans-2-butene, isobutene, 2-methyl-2-butene, and 2,3-dimethyl-2-butene. These results extend our knowledge of the replacement mechanism in O + olefin reactions, i.e., a methyl radical or a hydrogen atom can be expelled directly from the triplet biradical formed by an O atom addition to an olefin. Methyl substituted vinery radicals can also be produced by the release of a methyl radical from the 2-position carbon of an energized singlet aldehyde or ketone formed by a 1,2-migration of a hydrogen atom in the triplet biradical.