  We present predictions for the non-singlet Drell-Yan longitudinal spin cross
sections and spin asymmetry, $A_{LL}$, in proton-proton collisions at large
$p_T$ at the RHIC energy of $200\gev$ at next-to-leading order QCD. The higher
order corrections to the non-singlet polarized cross section,
$\sigma_{NS}^{LL}$, are sizeable and similar to those found for the unpolarized
cross section. The non-singlet asymmetry parameter, $A^{NS}_{LL}$, is very
stable against higher order corrections and is a direct measurement of the
non-singlet (i.e. valence) polarized quark distributions within the proton.
