  We investigate the influence of the boundary conditions on the scale
invariant critical level statistics at the metal insulator transition of
disordered three-dimensional orthogonal and two-dimensional unitary and
symplectic tight-binding models. The distribution of the spacings between
consecutive eigenvalues is calculated numerically and shown to be different for
periodic and Dirichlet boundary conditions whereas the critical disorder
remains unchanged. The peculiar correlations of the corresponding critical
eigenstates leading to anomalous diffusion seem not to be affected by the
change of the boundary conditions.
