  The superspace geometry of Chern-Simons forms is shown to be closely related
to that of the 3-form multiplet. This observation allows to simplify
considerably the geometric structure of supersymmetric Chern-Simons forms and
their coupling to linear multiplets. The analysis is carried through in U_K(1)
superspace, relevant at the same time for supergravity-matter couplings and for
chirally extended supergravity.
