  The quantum fluctuations of the quark condensate are calculated using a
regulated Nambu Jona-Lasinio model. The corresponding quantum fluctuations of
the chiral fields are compared to those which are predicted by an
''equivalent'' sigma model. They are found to be large and comparable in size
but they do not restore chiral symmetry. The restoration of chiral symmetry is
prevented by an ''exchange term'' of the pion field which does not appear in
the equivalent sigma model. A vacuum instability is found to be dangerously
close when the model is regulated with a sharp 4-momentum cut-off.
