  Partonic intrinsic transverse momentum can be essential for the explanation
of large single spin asymmetries in hadronic reactions in the framework of
perturbative QCD. The status of an ongoing program investigating in a
consistent way the role of intrinsic transverse momentum both in unpolarized
and polarized processes is discussed. We compute inclusive cross sections for
hadron and photon production in hadronic collisions and for Drell-Yan
processes; the results are compared with available experimental data in several
different kinematical situations.
