  Low-energy high-resolution neutrino-electron scattering experiments may play
an important role in testing the gauge structure of the electroweak
interaction. We propose the use of radioactive neutrino sources (e.g.
$^{51}$Cr) in underground experiments such as BOREXINO, HELLAZ and LAMA. As an
illustration, we display the sensitivity of these detectors in testing the
possible existence of extra neutral gauge bosons, both in the framework of E_6
models and of models with left-right symmetry.
