  This paper is a long write-up of ERATO. ERATO is a Monte Carlo event
generator describing four fermion production at LEP2 and beyond. All tree-order
processes leading to four fermions are included, taking into account all
relevant QCD contributions. QED higher order corrections are introduced via a
structure function approach, whereas weak corrections related to fermion loops
are also included. Special attention has been paid in studying the trilinear
gauge couplings, and all possible contributions, including the CP-violating
ones, have been implemented.
