We study the role of D-terms in supersymmetry (SUSY) breaking. By carefully
analyzing the SUSY multiplets containing various conserved currents in theories
with global symmetries, we obtain a number of constraints on the
renormalization group flow in supersymmetric field theories. Under broad
assumptions, these results imply that there are no SUSY-breaking vacua, not
even metastable ones, with parametrically large D-terms. This explains the
absence of such D-terms in models of dynamical SUSY-breaking. There is,
however, a rich class of calculable models which generate comparable D-terms
and F-terms through a variety of non-perturbative effects; these D-terms can be
non-abelian. We give several explicit examples of such models, one of which is
a new calculable limit of the 3-2 model.Comment: 34 pages, 2 figures; reference added, minor change