Mass transfer of tetrachloroethylene (PCE) gas, followed by a free-OH radical reaction in the liquid phase, was studied in a bubble column reactor equipped with a UV light source and containing aqueous H2O2 as the reacting medium. Degradation of PCE in the liquid phase was found to follow pseudo-first-order kinetics, and the optimal ratio of H2O2/PCE leading to the highest oxidation rate could be successfully obtained from the analysis of the steady-state OH radical concentration. Absorption of PCE gas was in the kinetic slow regime and could be predicted based on the ratio of the apparent rate constant of PCE liquid degradation to the volumetric mass transfer coefficient (kapp/K(L)a). The presence of small amounts of PCE in the liquid bulk had positive effect on the mass transfer over the range studied and need to be, taken into account.