  In this paper, we characterize the class of {\em contraction perfect} graphs
which are the graphs that remain perfect after the contraction of any edge set.
We prove that a graph is contraction perfect if and only if it is perfect and
the contraction of any single edge preserves its perfection. This yields a
characterization of contraction perfect graphs in terms of forbidden induced
subgraphs, and a polynomial algorithm to recognize them. We also define the
utter graph $u(G)$ which is the graph whose stable sets are in bijection with
the co-2-plexes of $G$, and prove that $u(G)$ is perfect if and only if $G$ is
contraction perfect.
