A theoretical study of the host...guest interactions in the intercalation compounds MF.XY and 2MF.XT (M = Li, K, Cs; X, Y = Cl, Br, I) is presented. A qualitative description of the bonding is obtained in the form of a band interaction diagram by using a Crystal Orbital Difference (GOD) analysis of extended Huckel tight-binding band calculations. Quantitative estimates of the host...guest interaction energies in these compounds are obtained from periodic Hartree-Fock (HF) calculations on the solids and molecular orbital calculations on a cluster model, including electron correlation through a second-order Moeller-Plesset (MP2) treatment. Periodic HF calculations correctly predict the trends in the structural and vibrational variations resulting from host...guest interactions, with formation energies of ca. 2 kcal/mol for the CsF.Br-2 and CsF.I-2 intercalates. General trends in the MF.XY family indicate that the intercalation compounds are not stable for M = K or Li and XY = Br-2, and that the host...guest interaction energy depends on the energy of the HOMO of the guest molecule XY and on its dipole moment.