The ab initio MO based lattice energy minimization method, which have been recently proposed, is applied to the calculation of the packing structures of methanol crystal, alpha- and beta-phases. We employed the correlated wavefunction level of theory, the second order Moller-Plesset perturbation theory (MP2), for the calculation of the lattice energy. The lattice parameters optimized at the MP2/6-31++G** level for alpha-phase were in good agreement with the experimental values and these for beta-phase were in moderate agreement with the experiment. The averaged relative errors of the calculated cell lengths were 0.9% and 6.2% for alpha- and beta-phases, respectively. (C) 2003 Elsevier Science B.V. All rights reserved.