  We calculate the next-to-leading order QCD corrections to the spin-dependent
cross section for single-inclusive hadron production in hadronic collisions.
This process will be soon studied experimentally at RHIC, providing a tool to
unveil the polarized gluon distribution $\Delta g$. We observe a considerably
improvement in the perturbative stability for both unpolarized and polarized
cross sections. The NLO corrections are found to be non-trivial, resulting in a
reduction of the asymmetry.
