  The gluon polarization $\Delta{G}/G$ is the key to a further clarification of
the spin structure of the nucleon. The COMPASS collaboration at CERN has set
out to undertake the direct determination of this quantity. It accesses the
gluon distribution via the photon-gluon fusion process (PGF) in scattering
polarized muons off a polarized deuteron target. And it explores three
different channels to tag the PGF: open charm production and high transverse
momentum (high p_T), in either electroproduction (Q^2 > 1 GeV^2) or quasi-real
photoproduction (Q^2 < 1 GeV^2).
  The high p_T quasi-real photoproduction channel yields the most precise
measurement. The result indicates that the gluon polarization is small. I
describe its experimental aspects and its theoretical framework, based on
PYTHIA. And I report on the preliminary results obtained in the other two
channels, and on the prospects for future analysis and data taking.
