  The role of intrinsic transverse momentum both in unpolarized and polarized
processes is discussed. We consider inclusive cross sections for pion
production in hadronic collisions and for Drell-Yan processes. We reanalyze
transverse single spin asymmetries (SSA) in inclusive pion production,
p(transv. polarized) p --> pion + X, in terms of Sivers effect and show its
contribution to A_{UL} in semi-inclusive DIS (SIDIS).
