Geometries for possible transition states and energy minima of the potential-energy surface for the reaction between BrO and ClO radicals and for conformers of ClOOBr peroxide have been identified and harmonic frequency calculations have been carried out at the second-order Moller-Plesset perturbation theory level using the 6-311++G(2d) and the 6-311++G(3df) basis sets. The energetics have been studied using the CCSD(T)/6-311++G(3df) methodology at the MP2 calculated geometries. The results assist in the qualitative understanding of the mechanism and the kinetics of the stratospherically important BrO + ClO reaction.