  We briefly describe the energy loss processes of ultrahigh energy protons,
heavier nuclei and gamma rays in interactions with the universal photon fields
of the Universe. We then discuss the modification of the accelerated cosmic ray
energy spectrum in propagation by the energy loss processes and the charged
cosmic ray scattering in the extragalactic magnetic fields. The energy lost by
the ultrahigh energy cosmic rays goes into gamma rays and neutrinos that carry
additional information about the sources of highest energy particles. The new
experimental results of the HiRes and the Auger collaborations are discussed in
view of the predictions from propagation calculations.
