The status of the gaugino condensation as the source of supersymmetry
breaking is reexamined. It is argued that one cannot have stable minim
a with broken supersymmetry in models where the dilaton is coupled onl
y linearly to the gaugino condensate. We show that the problems of the
gaugino condensate mechanism can be solved by considering non-standar
d gauge kinetic functions, created by non-perturbative effects, As an
example we use the principle of S-duality to modify the coupling of th
e gaugino condensate to effective supergravity (superstring) Lagrangia
ns. We show that such an approach can solve the problem of the runaway
dilaton and lead to satisfactory supersymmetry breaking in models wit
h a single gaugino condensate. We exhibit a general property of theori
es containing a symmetry acting on the dilaton and also shed some ligh
t on the question whether it is generically the auxiliary field of the
modulus T that dominates supersymmetry breaking.