We present the full next-to-next-to-leading order (NNLO) coefficient functions for the polarized cross section $dDelta sigma/dQ$ for the Drell-Yan process $p + pto l^+l^- + X$. Here $X$ denotes any inclusive hadronic state and $Q$ represents the invariant mass of the lepton pair. All QCD partonic subprocesses have been included provided the lepton pair is created by a virtual photon, which is a valid approximation for $Q<50$ GeV. Unlike the differential distribution w.r.t. transverse momentum the dominant subprocess for the integrated cross section is given by $q+bar q to gamma^* + X$ and its higher order corrections so that massive lepton pair production provides us with an excellent tool to measure the polarized anti-quark densities. Our calculations are carried out using the method of $n$-dimensional regularization by making a special choice for the $gamma_5$ matrix. We give predictions for double longitudinal spin asymmetry measurements at the RHIC.
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