  Pseudo-scalar and vector meson correlation functions were calculated at
temperatures below and above the deconfinement transition using ${\cal O}(a)$
improved Wilson fermions in quenched lattice QCD. The spectral functions were
reconstructed from the correlator given only at discrete points in Euclidean
time by means of the Maximum Entropy Method without a priori assumptions on the
spectral shape. The deviation of the spectral functions from the one of a
freely propagating quark anti-quark pair is examined above the critical
temperature. At 1.5 and 3 $T_c$ the vector spectral function yields an
enhancement of the dilepton rate over the Born rate in the energy interval $4 <
\omega/T < 8$ and a sharp drop at energies below 2-3 T.
