  We examine charge/colour breaking along directions in supersymmetric field
space which are F and D-flat. We catalogue the dangerous directions and include
some new ones which have not previously been considered. Analytic expressions
for the resulting constraints are provided which are valid for all patterns of
supersymmetry breaking. As an example we consider a recently proposed pattern
of supersymmetry breaking derived in Horava-Witten M-theory, and show that
there is no choice of parameters for which the physical vacuum is a global
minimum.
