Optimal structures, interaction energies and harmonic vibrational frequencies of the CH3OH... HCl dimer, mixed trimers 2CH(3)OH... HCl, and CH3OH... 2HCl have been determined from the supermolecular calculations with the aug-cc-pVDZ and the aug-cc-pVTZ basis sets. at the MBPT2 and CCSD(T) level. We located three low-energy configurations on the potential energy surface corresponding to H-bonded cyclic trimers 2CH(3)OH... HCl and two cyclic trimers CH3OH... 2HCl. The contribution of the three-body term represents as much as 25% for the total CCSD(T) interaction energy in the trimers. The calculations of the vibrational frequencies and infrared intensities for these complexes are presented to facilitate the frequency assignments of future experimental spectra. (C) 2004 Elsevier B.V. All rights reserved.