  We propose a stringy mechanism whereby a large hierarchy between symmetry
breaking scales is generated. This mechanism is based upon the existence of a
fifth dimension compactified on a segment. We focus on a simple supersymmetric
model with one massless Higgs field in the 3 of SU(3) and another one in the
$\bar 3$ on each four dimensional end-point of the fifth dimension. Along
supersymmetric flat directions the gauge symmetry is broken down to SU(2) due
to the vacuum expectation value of the Higgs fields on one of the end points.
The remaining massless mode on the other end point acquires a potential due to
a massive five dimensional state propagating between the end points. This
potential breaks the SU(2) symmetry at an exponentially suppressed scale
compared to the SU(3) breaking scale. The suppression factor depends
exponentially on the mass M of the massive state and the length $\pi R$ of the
fifth dimension. For reasonably large values of the length scale R one can
achieve a factor of order $M_{W}/M_GUT}$.
