  We first review the calculations of low invariant mass dilepton production in
relativistic heavy ion collisions, using effective hadronic Lagrangians. We go
through some of the theoretical techniques used in this kinematical region and
we consider some of the appropriate experimental measurements. Moving up to the
intermediate invariant mass region, we point out some of the uncertainties that
show up in theoretical estimates. Those originate mainly from off-shell
effects. Finally, as an application of hadronic chiral Lagrangians at finite
temperature, we compute the mass shifts and mixing of the omega and phi mesons
due to scattering from thermal pions.
