  The role of neutrinos in big bang nucleosynthesis is discussed. The bounds on
the number of neutrino families, neutrino degeneracy, parameters of neutrino
oscillations are presented. A model of chemically inhomogeneous, while
energetically smooth, universe created by inhomogeneous cosmological neutrino
asymmetry is described. Nucleosynthesis limits on production of right-handed
neutrinos are considered.
