  The usage of polarimetry and spin-correlation tests to determine the {\em
complete Lorentz structure} of the tau lepton's charged and neutral-current
couplings is reviewed. The emphasis is on tests for ``something'' in a $(V-A) +
$ ``something'' structure in ${J^{Charged}}_{Lepton}$ current, so as to bound
the scales $\Lambda$ for ``new physics" such as arising from tau weak
magnetism, weak electricity, and/or second-class currents. Tests for $T$ and
for $CP$ violation are discussed.
