  We present a complete analysis of the one loop electroweak corrections to
$e^-e^+\to\gamma\gamma, ~Z\gamma, ~ZZ$ in the Standard (SM) and the Minimal
Supersymmetric Standard Model (MSSM). Analytic expressions are written for the
contributions to the helicity amplitudes. Several observables accessible for
polarized or unpolarized beams and transverse, longitudinal or unpolarized
final states are computed. We show that in the few hundred GeV region, these
observables provide a test of the various SM or MSSM components. For the
dominant TT amplitude at high energy, the sensitivity to the details of the
various sectors disappears, but the energy dependence fixed by leading
logarithmic contributions, provides a model independent signature
discriminating SM from MSSM. Subdominant TL or LL amplitudes though, remain
sensitive to the details of the SM or MSSM sectors. Numerical illustrations are
given for energies up to several TeV. The analysis may also be used to search
for new physics characterized by anomalously strong interactions among the
neutral gauge bosons.
