The compound 2-butanol has been used to scavenge ≥95% of the OH radicals formed in the reactions of O3 with the alkenes 2,3-dimethyl-2-butene and 2-methyl-2-butene and with the monoterpenes α-pinene and sabinene at 296¿2 K and atmospheric pressure of air, with the OH radical formation yields from these O3 reactions being obtained from the amounts of 2-butanone formed. The rate constant for the reaction of the OH radical with 2-butanol was measured using a relative rate method; the rate constant was determined to be (9.2¿2.4)¿10-12 cm3 molecule-1 s-1 at 296¿2 K, where the indicated error includes the estimated overall uncertainties in the rate constant for the reference organic (cyclohexane). The formation yield of 2-butanone from the reaction of the OH radical with 2-butanol was determined to be 0.695¿0.073. Using this 2-butanone formation yield from the OH radical reaction with 2-butanol, the OH radical formation yields from the reactions of O3 with 2,3-dimethyl-2-butene, 2-methyl-2-butene, α-pinene, and sabinene were determined to be 0.80¿0.12, 0.93¿0.14, 0.76¿0.11, and 0.33¿0.06, respectively. These OH radical formation yields agree to within ¿25% with the yields previously derived using cyclohexane to scavenge OH radicals and measuring the amounts of cyclohexanone plus cyclohexanol formed. Our present OH radical formation yield for 2,3-dimethyl-2-butene is also in good agreement with the value of 0.7 previously reported from a comprehensive product study. ¿ American Geophysical Union 1996