High-resolution photoelectron spectra of F2, Cl2, Br2, I2, ICl and IBr are reported and interpreted in terms of the electronic structures of these molecules. Vertical and adiabatic ionization potentials as well as vibrational data are given for the ionized states arising from the removal of an electron from each molecular orbital. Where possible, these values are related to the emission spectra of the molecular ion and to the vacuum u.-v. spectra of the neutral species.