  We review the hadro-production data presently available on open charm and
beauty absolute production cross-sections, collected by experiments at CERN,
DESY and Fermilab. The published charm production cross-section values are
updated, in particular for the "time evolution" of the branching ratios. These
measurements are compared to LO pQCD calculations, as a function of the
collision energy, using recent parametrisations of the parton distribution
functions. We then estimate, including nuclear effects of the parton densities,
the charm and beauty production cross-sections relevant for measurements at SPS
and RHIC energies, in proton-proton, proton-nucleus and nucleus-nucleus
collisions. The calculations are also compared with measurements of single D
and B kinematical distributions, and DDbar pair correlations. We finish with
two brief comments, concerning the importance of beauty production as a
feed-down source of J/psi production, and open charm measurements performed
using leptonic decays.
