  We explore the implications of possible neutrino oscillations, as indicated
by the solar and atmospheric neutrino experiments, for the cold plus hot dark
matter scenario of large scale structure formation. We find that there are
essentially three distinct schemes that can accommodate the oscillation data
and which also allow for dark matter neutrinos. These include (i) three nearly
degenerate (in mass) neutrinos, (ii) non-degenerate masses with $\nu_\tau$ in
the eV range, and (iii) nearly degenerate $\nu_\mu-\nu_\tau$ pair (in the eV
range), with the additional possibility that the electron neutrino is
cosmologically significant. The last two schemes invoke a `sterile' neutrino
which is light (< or ~ eV). We discuss the implications of these schemes for
$\bar{\nu}_\mu - \bar{\nu}_e$ and $\nu_\mu - \nu_\tau$ oscillation, and find
that scheme (ii) in particular, predicts them to be in the observable range. As
far as structure formation is concerned, we compare the one neutrino flavor
case with a variety of other possibilities, including two and three degenerate
neutrino flavors. We show, both analytically and numerically, the effects of
these neutrino mass scenarios on the amplitude of cosmological density
fluctuations. With a Hubble constant of 50 km s$^{-1}$ Mpc$^{-1}$, a spectral
index of unity, and $\Omega_{baryon} = 0.05$, the two and three flavor
scenarios fit the observational data marginally better than the single flavor
scheme. However, taking account of the uncertainties in these parameters, we
show that it is premature to pick a clear winner.
