The Gaussian-3 (G3) and Gaussian-3X (G3X) models of theory have been used to calculate the thermochemical data for chlorine fluorides ClFn, n = 1-7, as well as for their singly charged cations and anions. The quantities calculated include the heats of formation (DeltaH(f)) and bond dissociation energies (DEs) of all of the species, as well as the ionization energies (IEs) and electron affinities (EAs) of the neutrals. By comparing the well-established experimental data of CIF and ClF3 with the G3 and G3X results, it is found that the G3X method yields more accurate DeltaH(f) values. In addition, the G3 values on the IEs and EAs for CIF and ClF3 are similar to the corresponding G3X results. On the basis of these findings, the G3X results are used to assess the sometimes conflicting experimental data. The fair to excellent agreement between the known experimental values and the G3X results also lends support to our predictions for the missing experimental thermochemical data of chlorine fluorides and their ions. Furthermore, with the results obtained in this work, a set of self-consistent thermochemical data for ClFn and their ions is proposed. Finally, the alternating patterns of the DeltaH(f), DE, IE, and EA values of the ClFn and their ions with system size n are rationalized in terms of the electronic configuration around the central Cl atom for the species involved.