  In the context of the field theory limit of superstrings, we consider an
almost realistic model of supersymmetry breaking by gaugino condensation which
includes, through nonperturbative corrections to the K\"ahler potential,
dilaton stabilization at a value compatible with a weak coupling regime.
Invariance under modular transformations is ensured through a Green-Schwarz
term and string threshold corrections, which lead to moduli stabilization at
the self-dual point. We are thus in a position to discuss several issues of
physical relevance: gravitino, dilaton and moduli masses, axion, soft
supersymmetry breaking parameters and gauge coupling unification.
