Photoelectron spectra have been obtained, by use of He 21·22 eV photons, for the tetrafluorides and tetrachlorides of carbon, silicon, and germanium, and for tin tetrachloride. The modified retarding grid instrument used is described in outline. Vertical ionization potentials (i.p.) and in some cases estimates of adiabatic i.p. also, are tabulated, and the observed bands have been assigned to a molecular orbital energy sequence which is the same for all seven compounds. The assignments are used to provide evidence in support of d-orbital participation in the bonding of all but the carbon halides, and particularly in the silicon halides.