  A poset P is called reversible if every order preserving bijective self map
of P is an order automorphism. P is called hereditarily reversible if every
subposet of P is reversible. We give a complete characterization of
hereditarily reversible posets in terms of forbidden subsets. A similar result
is stated also for preordered sets. As a corollary we extend the list of known
examples of hereditarily reversible topological spaces.
