  Quark-lepton symmetric models are a class of gauge theories motivated by the
similarities between the quarks and leptons. In these models the gauge group of
the standard model is extended to include a ``color'' group for the leptons.
Consequently, the quarks and leptons can then be related by a $Z_2$ discrete
quark-lepton symmetry which is spontaneously broken by the vacuum. Models
utilizing quark-lepton symmetry with acceptable and interesting collider
phenomenology have been constructed. The cosmological consequences of these
models are also discussed.
