  The SuperKamiokande data on atmospheric neutrinos imply that $\nu_{\mu}$ has
large (or even maximal) mixing. It is still open question whether this mixing
is the flavor one or mixing with singlet state (sterile neutrino). Several
tests exist to establish the channel of atmospheric neutrino oscillations.
Large mixing can be a property of the second and third generations, so that the
scheme with single large mixing is realized. It can be a generic property of
all leptons, thus leading to the bi-large or threefold large mixing schemes.
The ambiguity will be resolved by identification of solution of the solar
neutrino problem. In this review we consider phenomenology of various mixing
schemes. The key measurements which will allow us to make significant step in
reconstruction of the neutrino mass and flavor spectrum are discussed.
