  New experimental results on the spin dependent structure functions g_1 and
g_2 which are determined from deep-inelastic scattering experiments at CERN,
SLAC and DESY are reported. These results are used to evaluate the Bjorken sum
rule and the singlet axial charge a_0. Results are discussed in the framework
of next-to-leading order perturbative QCD. The role of the polarised gluons in
the interpretation of the results on a_0 is emphasised. New experiments which
aim to determine gluon polarisation are shortly described.
