The equilibrium geometries, relative stabilities, and vibrational properties (frequencies and intensities) of the HF-CH3Cl (1:1) and (HF)(2)-CH3Cl (1:2) complexes were reinvestigated at the MP2/Aug-cc-pVTZ level. The results are discussed in light of the results obtained in solid argon matrices by L. Andrews and co-workers and related to the bonding analysis. The stability and cooperative effects in the hydrogen bonding of the (HF)(2)-CH3Cl complex in its cyclic form are outlined.