MP2/6-311++G(2d,2p) and MP2/aug-cc-pVTZ calculations are used to analyze the interaction between hypochlorous acid (HOCI) and ozone. Six and five minima are located on the potential energy surface of HOCI center dot center dot center dot O-3 complexes at MP2/6-311++G(2d,2p) and MP2/aug-cc-pVTZ computational levels, respectively. The more strongly bound contains OH center dot center dot center dot O along with O center dot center dot center dot CI bond. The rest of the minima present in addition to the OH center dot center dot center dot O hydrogen bond, O center dot center dot center dot O and O center dot center dot center dot Cl interactions. Binding energies of the complexes corrected with BSSE lies in the range of 6 - 12 and 9 - 16 kJ mol(-1) at MP2/6-311++G(2d,2p) and MP2/aug-cc-pVTZ levels, respectively. The atom in molecules (AIM) theory was also applied to explain the nature of the complexes. (c) 2007 Elsevier B.V. All rights reserved.