The OCS + OH reaction occurs either via adduct formation or direct S-abstraction. We investigate OH oxidation of OCS using quantum chemical methods and find that the OC(OH)S adduct reacts rapidly with O-2 forming SOOH + CO2. SOOH rapidly dissociates under atmospheric conditions regenerating OH. We interpret earlier experimental results based on monitoring OH-loss, and find that OH-regeneration in presence of O-2 may explain the insensitivity of the reaction rate to pressure and O-2. We calculate a rate constant of 3.52 x 10(-16) cm(3) s(-1) at 10 Torr increasing to 7.20 x 10(-1)6 cm(3) s(-1) at 700 Torr. In addition we present a new experimental determination of the OCS + OH rate constant of (5.3 +/- 3.6) x 10(-15) cm(3) s(-1) at 296 K and 700 Torr using relative-rate technique. (C) 2017 Elsevier B.V. All rights reserved.