  We study the behavior of the rho vector mass in the context of the almost
baryon-free environment of an ultra-relativistic heavy-ion collision. We show
that rho scattering within the hadronic phase of the collision leads to a
temperature dependent, decrease of its intrinsic mass at rest, compared to the
value in vacuum. The main contributions arise from s-channel scattering with
pions through the formation of a1 resonances as well as with nucleons through
the formation of even parity, spin 3/2 [N(1720)] and 5/2 [Delta(1905)] nucleon
resonances. We show that it is possible to achieve a shift in the intrinsic
rho^0 mass of order - 40 MeV, when including the contributions of all the
relevant mesons and baryons that take part in the scattering, for temperatures
between chemical and kinetic freeze-out.
