I discuss chiral symmetry restoration in the chiral limit of QCD with
two quark flavours, focussing on its consequences for scalar and
pseudoscalar susceptibilities, and on the resulting constraints on the
Dirac spectrum. I show that U(1)_A breaking in the symmetric phase
requires the Dirac spectrum to develop peculiar features, including a
singular near-zero peak in the spectral density, and delocalisation of
the near-zero modes. I then discuss how these features relate to the
topological properties of gauge configurations.