  Results of the computer simulation of dilepton production from the expanding
pion gas created in ultrarelativistic Pb+Pb 160 GeV/n collisions are presented.
Finite size of the expanding pion gas influences invariant mass spectrum of
dileptons. Sensitivity of the shape of dilepton mass spectrum to the initial
stage of the pion gas is discussed. Second order asymmetry in azimuthal
distribution of dileptons is predicted for non-central collisions.
Non-equilibrium nature of the pion gas expansion is found to exhibit itself in
rapidity distribution of produced dilepton pairs.
