  Possible breakdown of the universality of the gravitational couplings to
different neutrino flavors can be tested in long-baseline neutrino-oscillation
experiments, such as a proposed experiment at SOUDAN 2 or one at the DUMAND
project. Such a breakdown could be detected with sensitivity to the order of
$10^{-14}$ or $10^{-15}$. For generic case of neutrino oscillations, it is
emphasized that one can identify the spin of the particle which mediates the
force causing the oscillation, by investigating the energy spectrum of the
outgoing charged leptons. (based on talk presented at the Workshop on General
Relativity and Gravitation held at Univ. of Tokyo, January 17-20, 1994)
