  We consider the factorization properties of on-shell QCD amplitudes with
massive partons in the limit when all kinematical invariants are large compared
to the parton mass and discuss the structure of their infrared singularities.
The dimensionally regulated soft poles and the large collinear logarithms of
the parton masses exponentiate to all orders. Based on this factorization a
simple relation between massless and massive scattering amplitudes in gauge
theories can be established. We present recent applications of this relation
for the calculation of the two-loop virtual QCD corrections to the
hadro-production of heavy quarks.
