  I discuss the possibility of neutrino oscillation in presence of gravity. In
this respect I consider the propagation of neutrinos in the early phase of
universe and around black holes. It is seen that whether the rest masses of a
neutrino and corresponding anti-neutrino are considered to be same or not due
to space-time curvature effect non-zero oscillation probability between the
neutrino and anti-neutrino states comes out. Therefore I can conclude that
under gravity neutrino oscillation takes place which is independent of their
rest mass.
