  Steep dispersion of opposite signs in driven degenerate two-level atomic
transitions have been predicted and observed on the D2 line of 87Rb in an
optically thin vapor cell. The intensity dependence of the anomalous dispersion
has been studied. The maximum observed value of anomalous dispersion [dn/dnu ~=
-6x10^{-11}Hz^{-1}] corresponds to anegative group velocity V_g ~= -c/23000.
