  We discuss some recent developments concerning the nucleon's helicity parton
distribution functions: New preliminary data from jet production at RHIC
suggest for the first time a non-vanishing polarization of gluons in the
nucleon. SIDIS measurements at COMPASS provide better constraints on the
strange and light sea quark helicity distributions. Single-longitudinal spin
asymmetries in W-boson production have been observed at RHIC and will
ultimately give new insights into the light quark and anti-quark helicity
structure of the nucleon.
