Asymptotic QCD perturbation theory and transverse momentum distributions in Drell-Yan processes

The authors shortly review to which extent the QCD asymptotic peturbative expansion can be applied to processes which are not light-cone dominated. The transverse momentum distribution of large mass muon pairs produced in hadron-hadron collisions is very good test of these ideas. At present energies, however, non-perturbative effects like the presence of an intrinsic transverse momentum of partons are still relevant. (author)