An infrared study of ¹²C¹⁶O and ¹³C¹⁶O adsorbed at 77 K on ZnO, TiO₂, BeO, Al₂O₃, and SiO₂ has provided details on two kinds of interactions between the adsorbed molecules which account for the dependence of the spectra on surface coverage. The observed v_co values, which for coordinatively bonded molecules are 50-100 cm^-1 higher compared with gaseous CO, are lowered significantly (up to 30 cm^-1) on increasing coverage as a result of a "chemical" effect, namely the weakening of the electron-donating ability of metal ion after occupation of the adjacent sites with adsorbed molecules. The fine structure of the CO ZnO spectrum reflects the stepwise character of this process. The second type of interaction is dipole coupling. This causes a comparatively weak upward shift (up to 6 cm^-1), partly counteracting the "chemical" effect.