  I discuss different models which predict changes in the mass of the thermal
$\rho$ field. I emphasize that while the predictions are strongly model
dependent, nevertheless substantial shifts in the thermal $\rho$ mass are
expected to occur at the point of phase transition. As long as the thermal
$\rho$ peak does not become too broad, this should provide a striking signature
of the existence of a phase transition. (Based upon a talk presented at Quark
Matter '95, Monterey, CA, Jan., 1995.)
