  We perform a model-independent analysis of the spontaneously broken phase of
an $SU(2)\times U(1)$ supersymmetric gauge theory, by using a non-linear
parametrization of the Goldstone sector of the theory. The non-linear variables
correspond to an $SL(2,C)$ superfield matrix in terms of which a non-linear
Lagrangian can be constructed, and the pattern of supersymmetry breaking
investigated. The supersymmetric order parameter is the V.E.V. of the neutral
pseudo-Goldstone boson. Some applications of this technique are considered, in
relation to the minimal supersymmetric standard model, and to determine the
$g-2$ of the $W$-bosons in the limit of large top mass.
