  The concept of perturbative gauge invariance formulated exclusively by means
of asymptotic fields is generalized to massive gauge fields. Applying it to the
electroweak theory leads to a complete fixing of couplings of scalar and ghost
fields and of the coupling to leptons, in agreement with the standard theory.
The W/Z mass ratio is also determined, as well as the chiral character of the
fermions. We start directly with massive gauge fields and leptons and,
nevertheless, obtain a theory which satisfies perturbative gauge invariance.
