We have calculated approximate room temperature rate constants for mtramolecular hydrogen shaft rsomerizatrons of alkyd, alkovy and alkylperoxy radrcal mtermediates in photochemical smog and found that alkoxy radicals wrth 6 hydrogcns appear to undergo I,5 hydrogen shifts at ambient conditions Product drstrrbutions observed during irradiations of alkane (n-butane, n-pentane and n-hexant*)-NO, -air systems in two quite different J 6000~liter environmental chambers were found to be consistent with this predictron. For example. in the n-pentane-NO, -air system the observed large yields of f-pentanone reIatrve co 2-pentanone were consistent with room temperature rate constants which we have estimated for the axrespondzng hydrogen shrft rsomrrrzatrons Whrle such rsomerizatrons have been well recognized in studies of free radicals dnr! hrgh temperature hydrocarbon oxidations, they are not taken mto account m current kinetic mechanisms for alkane oxidation under ambient atmospheric condrtrons This has unplications for the construction of computer models of photochemical smog formatron.