Implications of solar and atmospheric neutrinos

The importance of non-zero neutrino mass as a probe of particle physics, as trophysics, and cosmology is emphasized. The present status and future pros pects for the solar and atmospheric neutrinos are reviewed, and the implica tions for neutrino mass and mixing in 2, 3, and 4-neutrino schemes are disc ussed. The possibilities for significant mixing between ordinary and light sterile neutrinos are described.