The valence shell ionization energies of a series of alkenyl-and alkynylfluorocyclotriphosphazenes have been determined using ultraviolet photoelectron spectroscopy. In the alkenylphosphazene series, the effect of substituent variation on both the olefin and the cyclophosphazene ring have been examined. The data have been consistently interpreted in terms of a model in which phosphazene substituent effects are exclusively transmitted through polarization of the endo- and exocyclic sigma bonds.