  We present a calculation of the next-to-leading order QCD corrections to the
partonic cross sections contributing to single-inclusive high-p_T hadron
production in collisions of transversely polarized hadrons. We use a recently
developed projection technique for treating the phase space integrals in the
presence of the cos(2Phi) azimuthal-angular dependence associated with
transverse polarization. Our phenomenological results show that the double-spin
asymmetry A_TT^pi for neutral-pion production is expected to be very small for
polarized pp scattering at RHIC and could be much larger for the proposed
experiments with an asymmetric pbar-p collider at the GSI
