  We account for the solar and atmospheric neutrino problems by introducing
maximal mixing between conventional and sterile neutrino partners. We achieve
this by invoking a seesaw-like mechanism which not only provides us with
maximally mixed neutrino/sterile-neutrino mass eigenstates but also accounts
for the relative suppression of the neutrino masses compared to the charged
fermion masses. In obtaining such an extended seesaw mechanism we are required
to introduce a new U(1) global symmetry together with an extended Higgs sector.
