  We present a review of cosmological nucleosynthesis (CN) with neutrino
oscillations, discussing the different effects of oscillations on CN, namely:
increase of the effective degrees of freedom during CN, spectrum distortion of
the oscillating neutrinos, neutrino number density depletion, and growth of
neutrino-antineutrino asymmetry due to active-sterile oscillations. We discuss
the importance of these effects for the primordial yield of helium-4.
  Primordially produced He-4 value is obtained in a selfconsistent study of the
nucleons and the oscillating neutrinos. The effects of spectrum distortion,
depletion and neutrino-antineutrino asymmetry growth on helium-4 production are
explicitly calculated.
  An update of the cosmological constraints on active-sterile neutrino
oscillations parameters is presented, giving the values: delta m^2 sin^8 (2
theta) < 1.5 x 10^{-9} eV^2 for delta m^2 > 0, and |delta m^2| < 8.2 x 10^{-10}
eV^2 at large mixing angles for delta m^2 < 0. According to these constraints,
besides the active-sterile LMA solution, also the active-sterile LOW solution
to the solar neutrino problem is almost totally excluded.
