The high resolution photoelectron spectra of phosgene and thiophosgene have been obtained and, in each case, all ionization potentials up to 21.2 eV determined. The spectra are interpreted in terms of the molecular orbital structures and it is concluded that there is a strong interaction between the chlorine pπ "lone pair" electrons and those in the C=O or C=S π bond. The measured ionization potentials are compared with those calculated by the CNDO/2 method and with those obtained for similar molecules.