  Theories with gauge-mediated supersymmetry breaking provide an interesting
alternative to the scenario in which the soft terms of the low-energy fields
are induced by gravity. These theories allow for a natural suppression of
flavour violations in the supersymmetric sector and have very distinctive
phenomenological features. Here we review their basic structure, their
experimental implications, and the attempts to embed them into models in which
all mass scales are dynamically generated from a single fundamental scale.
