The peracid oxidation of tetramethylallene, 1,1-dimethylallene, and 1,2-cyclononadiene has been studied. The products of these reactions are rationalized in terms of initial formation of an aliene oxide followed by competitive partitioning of this reactive species between valence isomerism to the related cyclopropanone and further oxidation to a dioxaspiropentane derivative. In addition to combining with the carboxylic acid generated during the oxidation to produce -acyloxy ketones the cyclopropanones suffer further reaction with peracid to yield /3-lactones or undergo "oxidative decarbonylation" to the corresponding olefins which are usually transformed into their epoxides under the reaction conditions. The dioxaspiropentanes also add carboxylic acid yielding -acyloxy a'-hydroxy ketones. Thus, an excess of peracetic acid in buffered methanol gives 1, 8, and 12 as important products from tetramethylallene. A similar reaction under acidic conditions yields only 9. 1,2-Cyclononadiene is transformed to 20, 22, 23, and cyclooctene by peracid in methylene chloride. 1,1-Dimethylallene gives 30, 31, 32, and 33 under these conditions, but only acetone and methyl acetate in methanol solvent.