  We propose a model of suppression of large $p_T$-pions in heavy ion
collisions based on the interaction of the large $p_T$ pion with the dense
medium created in the collision. The model is practically the same as the one
previously introduced to describe $J/\psi$ suppression. Both the $p_T$ and the
centrality dependence of the data are reproduced. In deuteron-gold collisions,
the effect of the final state interaction with the dense medium turns out to be
negligibly small. Here the main features of the data are also reproduced both
at mid and at forward rapidities.
