  A review of the soft supersymmetry-breaking parameters and the $\mu$ term
arising in superstring models is performed paying special attention to their
phenomenological implications. In particular, the violation of the scalar mass
universality which may lead to dangerous flavor changing neutral current
phenomena and the existence of charge and color breaking minima are discussed.
Finally, quadratically-divergent loop effects by pure supergravity interactions
on soft parameters and the $\mu$ term are also reviewed and applied to
superstring models. They provide several new sources of the $\mu$ term,
naturally of order the weak scale, but also may lead to non--universal soft
terms.
