  We discuss the relation between the highest energy cosmic rays
  (UHECR) and UHE neutrinos. The neutrinos produced in the sources of optically
thin astrophysical sources have been linked to the UHECR emissivity of the
Universe. The fluxes of cosmogenic neutrinos, generated in propagation by
UHECR, also reflect the acceleration of these particles, the maximum
acceleration energy, and the cosmological evolution of their sources.
