  Anomalous U(1) gauge symmetries appear frequently both in heterotic and type
I/type II string theory. In the heterotic case we find at most a single
anomalous U(1), while in open string theories several such symmetries can
appear. We review the properties of the anomalous gauge bosons, the appearance
of Fayet-Iliopoulos terms and the concept of heterotic-type I duality.
Phenomenological applications of these symmetries might be different in the
type I/type II case compared to the heterotic one.
