  The critical behaviour of 3-dimensional disordered systems with magnetic
field is investigated by analyzing the spectral fluctuations of the energy
spectrum. We show that in the thermodynamic limit we have two different
regimes, one for the metallic side and one for the insulating side with
different level statistics. The third statistics which occurs only exactly at
the critical point is {\it independent} of the magnetic field. The critical
behaviour which is determined by the symmetry of the system {\it at} the
critical point should therefore be independent of the magnetic field.
