  I present a unified calculation of soft-gluon corrections to hard-scattering
cross sections through next-to-next-to-next-to-leading order (NNNLO). Master
formulas are derived, from a threshold resummation formalism, that can be
applied to total and differential cross sections for hard-scattering processes
in hadron colliders. I also present numerical results for charged Higgs
production at the LHC where these corrections are large, and for top quark
production at the Tevatron where these corrections greatly reduce the scale
dependence of the cross section.
