  We address the mass ranges of new neutral gauge bosons and constraints on the
accompanying exotic particles as predicted by a class of superstring models.
Under certain assumptions about the supersymmetry breaking parameters we show
that breaking of an additional U(1)' symmetry is radiative when the appropriate
Yukawa couplings of exotic particles are of order one, analogous to the
radiative breaking of the electro-weak symmetry in the supersymmetric standard
model due to the large top-quark Yukawa coupling. Such large Yukawa couplings
occur for a large class of string models. The Z' and exotic masses are either
of O(M_Z), or of a scale intermediate between the string and electro-weak
scales. In the former case, M_Z'=O(1 TeV) may be achievable without excessive
fine tuning, and is within future experimental reach. (This paper is a summary,
with a more phenomenological emphasis and additional discussion, of the results
in our earlier article "Implications of Abelian Extended Gauge Structures from
String Models", hep-ph/9511378.)
