The reactants, products, and the transition state for the reaction 1O3 + 2OH = 3O2 + 2HOO have been investigated using ab initio molecular orbital theory at the DFT level using the Perdew-Wang functional. Geometry optimizations and vibrational frequency calculations have been performed on all reactants, products, and the transition state at the pw91pw91/6-31+G* levels. Additional calculations have been carried out using the same levels of theory and basis sets for the reaction 2HOO + 3O = 2HO + 3O2. These calculations allow us to estimate the rate of these reactions and their importance in ozone depletion processes