The recently approved COMPASS experiment attempts a measurement of the
gluon polarization around eta similar or equal to 0.1 with a precisio
n of delta(Delta g/g) similar or equal to 0.1. The experiment uses ope
n charm muo-production and large P-T hadron pairs to tag the photon-gl
uon fusion process. COMPASS will also cover a rich spin-physics progra
m in polarized DIS.