Spin Structure of the Nucleon

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.