  We studied polarization effects in tau production by neutrino-nucleon
scattering. Quasi-elastic scattering, $Delta$ resonance production and deep
inelastic scattering processes are taken into account for the CERN-to-Gran
Sasso projects. We show that the tau produced by neutrino has high degree of
polarization, and its spin direction depends non-trivially on the energy and
the scattering angle of tau in the laboratory frame.
