OH radical formation yields from the reaction of ozone with several cycloalkenes were measured using small amounts of fast-reacting aromatics and aliphatic ethers to trace OH formation. Measured OH yields are much higher than for acyclic analogues. The yields are 0.62 +/- 0.15, 0.54 +/- 0.13, 0.36 +/- 0.08, and 0.91 +/- 0.20 for cyclopentene, cyclohexene, cycloheptene, and 1-methylcyclohexene, respectively. Density functional theory calculations at the B3LYP/6-31G(d,p) level are presented to aid in understanding the trends observed. Theory indicates that the OH production from cycloalkenes is largely controlled by the transition states for the cycloreversion of the primary ozonide.