Spin physics at short distances

In the framework of perturbative gauge theories spin effects take a particular simple form when the energy is large compared to the relevant rest masses. Polarization studies may thus offer very interesting experimental tests when perturbation calculations can be justified, i.e., at short distance. The purpose of this article is to present spin effects in reactions involning large momentum transfers and topical aspects of spin physics, with their emphasis on current attempts at relating hadron and quark polarization. (author)