  The total cross-section of the $\gamma \gamma \to 4 $ leptons process is
known to have a large constant value at high energy, but a complete and exact
calculation of related differential spectra does not exist yet. However a
complete study of the process is important at NLC for luminosity measurements
or for background estimations. We here report on our various steps in that
direction, including the implementation of a first new calculation of helicity
amplitudes in a Monte-Carlo generator.
