  The prediction of cross sections for nuclei far off stability is crucial in
the field of nuclear astrophysics. In recent calculations the nuclear level
density -- as an important ingredient to the statistical model
(Hauser-Feshbach) -- has shown the highest uncertainties. We present a global
parametrization of nuclear level densities based on the back-shifted Fermi-Gas
formalism. Employment of an energy-dependent level density parameter $a$ and
microscopic corrections from a recent FRDM mass formula by M\"oller et al.\
leads to a highly improved fit of level densities at the neutron-separation
energy in the mass range $20\le A \le 245$. The importance of using proper
microscopic corrections from mass formulae is emphasized. The resulting level
description is well suited for astrophysical applications.
  The level density can also provide clues to the applicability of the
statistical model which is only correct for a high density of excited states.
Using the above description one can derive a ``map'' for the applicability of
the model for reactions of stable and unstable nuclei with neutral and charged
particles.
