  The mass shift $\Delta m_{\rho}$ and width broadening $\Delta\Gamma_{\rho}$
of $\rho$ mesons produced in heavy ion collisions is estimated using a general
formula which relates the in-medium mass shift of a particle to the real part
of the forward scattering amplitude ${\rm Re} f(E)$ of this particle on
constituents of the medium and $\Delta\Gamma$ to the corresponding cross
section. It is found that in high energy ($E/A \ga 100~$GeV) heavy ion
collisions the $\rho$ width broadening is large and $\rho$ (or $\omega$) peak
could hardly be observed in $e^+e^-(\mu^+\mu^-)$ effective mass distributions.
In low energy collisions ($E/A \sim$ a few GeV) a broad (a few hundred MeV)
enhancement is expected at the position of the $\rho$ peak.

High Energy Physics - Phenomenology;Nuclear Theory