  It is possible for the SM fields to propagate into one or more large extra
compact dimensions. Such fields have associated KK excitations that produce
additional contributions to the SM processes. We calculate the effects that
these KK excitations have on cross sections for $e^{+}e^{-}$ collider processes
in a model in which the SM gauge bosons, and perhaps the Higgs, can propagate
into one TeV$^{-1}$-size extra compact dimension. Specifically, we consider
muon pair production, Bhabha scattering, dijet production, Higgs production,
and single-photon production. At prospective high energy $e^{+}e^{-}$
colliders, we find significant deviations from the SM cross sections: For
example, a 600 GeV collider produces a 20% reduction in the cross section for
muon pair production as compared to the SM for a compactification scale of 3.5
TeV. The effect is much smaller at LEP2 energies, where the compactification
scale must be lower than 2 TeV in order to produce a 6% effect.
