The bimolecular rate constants, k OH+ β -ionone (118±30)×10 −12 cm 3 molecule −1 s −1 and kO3+β‐ionone, (0.19±0.05)×10 −16 cm 3 molecule −1 s −1 , were measured using the relative rate technique for the reaction of the hydroxyl radical (OH) and ozone (O 3 ) with 4-(2,6,6-trimethyl-1-cyclohexen-1-yl)-3-buten-2-one (β-ionone) at 297±3K and 1atm total pressure. To more clearly define part of β-ionone's indoor environment degradation mechanism, the products of the β-ionone+OH and β-ionone+O 3 reactions were also investigated. The identified β-ionone+OH reaction products were: glyoxal (ethanedial, HC(=O)C(=O)H), and methylglyoxal (2-oxopropanal, CH 3 C(=O)C(=O)H) and the identified β-ionone+O 3 reaction product was 2-oxopropanal. The derivatizing agents O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) and N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) were used to propose 2,6,6-trimethylcyclohex-1-ene-1-carbaldehyde as the other major β-ionone+OH and β-ionone+O 3 reaction product. The elucidation of this other reaction product was facilitated by mass spectrometry of the derivatized reaction products coupled with plausible β-ionone+OH and β-ionone+O 3 reaction mechanisms based on previously published volatile organic compound+OH and volatile organic compound+O 3 gas-phase reaction mechanisms. The additional gas-phase products observed from the β-ionone+OH reaction are proposed to be the result of cyclization through a radical intermediate.