  Local conditions on boundaries of $C^\infty$ Levi-flat hypersurfaces, in case
the boundary is a generic submanifold, are studied. For nontrivial real
analytic boundaries we get an extension and uniqueness result, which forces the
hypersurface to be real analytic. This allows us to classify all real analytic
generic boundaries of Levi-flat hypersurfaces in terms of their normal
coordinates. For the remaining case of generic real analytic boundary we get a
weaker extension theorem. We find examples to show that these two extension
results are optimal. Further, a class of nowhere minimal real analytic
submanifolds is found, which is never the boundary of even a $C^2$ Levi-flat
hypersurface.
