  The quantitative description of the effects of nuclear dynamics on the
measured neutrino-nucleus cross sections -- needed to reduce the systematic
uncertainty of long baseline neutrino oscillation experiments -- involves
severe difficulties. Owing to the uncertainty on the incoming neutrino energy,
different reaction mechanisms contribute to the cross section measured at fixed
energy and scattering angle of the outgoing lepton, and must therefore be
consistently taken into account within a unified model. We review the
theoretical approach based on the impulse approximation and the use of
realistic nucleon spectral functions, allowing one to describe a variety of
reaction mechanisms active in the broad kinematical range covered by neutrino
experiments. The extension of this scheme to include more complex mechanisms
involving the two-nucleon current, which are believed to be important, is also
outlined. The impact of nuclear effects on the determination of neutrino
oscillation parameters is illustrated by analyzing the problem of neutrino
energy reconstruction.
