Attempts to understand g1(x) and g2(x)

The present theoretical understanding of the polarized nucleon structure functions is reviewed. The results of the European Muon Collaboration forg ₁ ^p (x) have generated an enormous theoretical activity, resulting in a large number of possible explanations. The presently available data are not sufficient to decide between them, but much improved experiments are planned for the next years. The possibility of an anomalous gluon contribution is most interesting on theoretical grounds. Finally we discussg ₂(x) which is extremely model dependent and thus could allow a clear decision between the various models proposed. Its measurement requires, however a much improved experimental precision.