  Anomalous U(1) gauge symmetries in type II orientifold theories show some
unexpected properties. In contrast to the heterotic case, the masses of the
gauge bosons are in general of order of the string scale even in the absence of
large Fayet-Iliopoulos terms. Despite this fact, the notion of heterotic-type
II orientifold duality remains a useful concept, although this symmetry does
not seem to hold in all cases considered. We analyse the status of this duality
symmetry, clarify the properties of anomalous U(1) gauge symmetry in the
orientifold picture and comment on the consequences for phenomenological
applications of such anomalous gauge symmetries.
