The potential energy surface (PES) for the H2O + CCl2 reaction was investigated at the ab initio SCF and MP2 levels of theory, employing the DZP basis set, in order to determine the mechanism of basic aqueous decomposition of CCl2. Several possible pathways were considered, including reactions with other H2O molecules and OH-. We have found that the first step corresponds to insertion of CCl2 into the O-H bond of water, resulting in the CHCl2OH species. This molecule loses HCl in one elimination reaction catalyzed by OH-, forming ClCHO. Again, OH- catalyzes the elimination of other HCl, resulting in CO, the decomposition product. The first step is the slow one, and we have used transition-state theory to estimate the rate constant for the aqueous decomposition of CCl2, The obtained rate constant was used for building a general picture of CHCl3, decomposition in basic aqueous solution. The results of the present study are in agreement with experimental observations.