Hydrogen abstraction reactions between chloromethanes and the hydroxyl radical have been investigated by using ab initio molecular orbital theory. Geometry optimizations and vibrational frequency calculations have been performed for all the reactants, products, and transition states at the MP2=full/6-311G(d,p) level. Subsequently, single point energy calculations have been carried out at the MP2=full/6-311G(2df,2p) and QCISD(T)/6-311G(2df,2p) levels for all the species. The transition state theory including the tunneling contributions has been used for estimating the rate constants for the hydrogen abstraction. The results obtained from our PMP2 and QCISD(T) calculations with the larger 6-311G(2df,2p) basis set have been found to be in good agreement with the available experimental values.