[en] The infrared spectra of the ¹²C, ¹³C, and ¹⁴C isotopic species of CF₄ have been observed at a resolution of 0.06 cm^-1. In addition to the fundamentals ν₃ and ν₄ a number of combination bands have been observed. Using these results, combined with Raman data in the literature, we have calculated the quadratic valence force field, in terms of force constants as well as compliance constants, with considerably better precision than previously obtained. Interaction displacement coordinates have been calculated and show that stretching one CF bond leads, for minimum energy near equilibrium, to opening up of the angles between the other three bonds as well as to their contraction