  An overview on the present observational status and phenomenological
understanding of cosmic rays above 10^16 eV is given. Above these energies the
cosmic ray flux is expected to be gradually dominated by an extra-galactic
component. In order to investigate the nature of this transition, current
experimental activities focus on the measurement of the cosmic ray flux and
composition at the 'ankle' or 'dip' feature at several EeV. At the ultra high
energy end of the spectrum, the flux suppression above 50 EeV is now well
established by the measurements of HiRes and the Pierre Auger Observatory and
we may enter the era of charged particle astronomy.
