Five minimum energy structures have been identified for dichlorine hexoxide and ab initio calculations have been performed on these isomers at the 6-31G * and MP2 * levels. Among the five structures, the oxygen-bridged structure and a symmetrical dimer containing a Cl-Cl bond were found to be stable. Normal mode analysis has been carried out on the stable conformers. The relative strength of the O 3 Cl-O and O-ClO 2 bonds of the oxygen-bridged structure is discussed on the basis of their vibrational frequencies. In addition, the paper focuses attention on the great importance of the reaction 2OClO + 2O 3 → Cl 2 O 6 + 2O 2 . The implications of these results to the chemistry of stratospheric ozone depletion are delineated.