  The RHIC facility at BNL will be operating soon, part of the year, as a
polarized proton-proton collider. This will allow the undertaking of a vast
spin physics programme, mainly by the two large detectors PHENIX and STAR. We
review some theoretical aspects of this research programme which will allow,
firstly to improve our present knowledge on polarized quark, gluon and sea
distributions in a nucleon, secondly to perform novel QCD spin tests and
finally, perhaps, to uncover some new physics.
