Angle-resolved photoelectron spectroscopy has become one of the most important tools for studying the electronic properties in solids and at surfaces. From the kinematics of the photoemission process the energy versus wave vector relation, E (k) can now be determined routinely provided tunable photon sources are available. Much less attention was focused to the spectroscopic information on electron correlation effects that may be extracted from lineshapes and linewidths, respectively. In fact the determination of "intrinsic" lineshape is hampered by several effects like broadening by finite spectrometer resolution, electron-photon interactions and the influence of structural defects in the bulk or at the sample surface. We report on ecent progress and discuss the present state of the art and experimentalists point of view.
