  Using the linear multiplet formulation for the dilaton superfield, we
construct an effective lagrangian for hidden-sector gaugino condensation in
string effective field theories with arbitrary gauge groups and matter.
Nonperturbative string corrections to the K\"ahler potential are invoked to
stabilize the dilaton at a supersymmetry breaking minimum of the potential.
When the cosmological constant is tuned to zero the moduli are stabilized at
their self-dual points, and the vev's of their F-component superpartners
vanish. Numerical analyses of one- and two-condensate examples with massless
chiral matter show considerable enhancement of the gauge hierarchy with respect
to the E_8 case. The nonperturbative string effects required for dilaton
stabilization may have implications for gauge coupling unification. As a
comparison, we also consider a parallel approach based on the commonly used
chiral formulation.
