Three different attacks of (3)Sigma(g) O-2 on the hydroxycyclohexadienyl radical intermediate I (generated from the reaction of OH. with benzene) have been studied by Density Functional Theory. Both abstraction by O-2 of the hydrogen gem to OH in I (affording phenol) and O-2 addition to the pi-delocalized system of I (producing a hydroxycyclohexadienyl peroxyl radical intermediate) appear to be very viable, with Delta H-double dagger = 3-4 kcal mol(-1). The former reaction is exothermic by 27 kcal mol(-1), the latter only by 1 kcal mol(-1). In contrast, a recently repropounded pathway, which would lead to benzene oxide/oxepin, via hydrogen abstraction from the hydroxyl in I operated by O-2, appears not to be competitive, showing a significantly higher barrier (Delta H-double dagger = 32 kcal mol(-1)). Benzene oxide and oxepin are estimated to lie 21 and 19 kcal mol(-1) above I, respectively.