A thermal desorption particle beam mass spectrometer has been used to investigate the products and mechanisms of secondary organic aerosol formation from reactions Of O-3 with cyclohexene, cycloheptene, cyclooctene, and cyclodecene in the presence of alcohols. Alkoxyhydroperoxy aldehydes formed through reactions of stabilized Criegee intermediates with alcohols have been identified by comparison of aerosol mass spectra with those of standards synthesized in solution. These compounds can subsequently isomerize through an intramolecular reaction between the hydroperoxyl and carbonyl groups to form a cyclic peroxyhemiacetal. For example, in the reaction Of O-3 with cyclodecene in the presence of 1-propanol the product of the reaction of the stabilized Criegee intermediate with 1-propanol is 10-n-propoxy-10-hydroperoxydecanal, which can then cyclize to 1-hydroxy-4-n-propoxy-2,3-dioxacyclododecane. Experiments performed by monitoring reactions of alkoxyhydroperoxy aldehyde standards added to the environmental chamber indicate that the cyclization reaction occurs in the gas phase, but apparently not in the particle phase, and occurs under thermal conditions. The alkoxyhydroperoxy aldehydes appear to undergo little, if any, intermolecular reaction to form dimers or polymeric peroxyhemiacetals.