The polar tensors of CFCl3, CF2Cl2, and CF3Cl determined from experimental infrared intensities are reported. The sign ambiguities in the dipole moment derivatives are resolved by comparing alternative polar tenser solutions with the results of MP2/6-311+G(3d) molecular orbital calculations using bidimensional principal component projections of the polar tenser spaces. The carbon mean dipole moment derivatives of-the fluorochloromethanes are in good agreement with the values predicted by an electronegativity model equation obtained from both fluoro- and chloromethane polar tenser data. These values are shown to be intermediate to those expected on the basis of separate fluoro- and chloromethane models. The mean dipole moment derivatives of the fluorine and chlorine atoms vary with the degree of fluorine-chlorine substitution. This contrasts with the almost constant values of these quantities already reported for the fluoro- and chloromethanes.