  The application of the exact renormalisation group to symmetric as well as
asymmetric many-fermion systems with a short-range attractive force is studied.
  Assuming an ansatz for the effective action with effective bosons, describing
pairing effects a set of approximate flow equations for the effective coupling
including boson and fermionic fluctuations has been derived. The phase
transition to a phase with broken symmetry is found at a critical value of the
running scale. The mean-field results are recovered if boson-loop effects are
omitted. The calculations with two different forms of the regulator are shown
to lead to a similar results. We find that, being quite small in the case of
the symmetric many-fermion system the corrections to mean field approximation
becomes more important with increasing mass asymmetry.
