  We show that massive lepton-pair production, the Drell-Yan process, should be
a good source of independent constraints on the polarized gluon density, free
from the experimental and theoretical complications of photon isolation that
beset studies of prompt photon production. We provide predictions for the
spin-averaged and spin-dependent differential cross sections as a function of
transverse momentum $Q_T$ at energies relevant for the Relativistic Heavy Ion
Collider (RHIC) at Brookhaven.
