  A sequential fourth generation of quarks and leptons is allowed by precision
electroweak constraints if the mass splitting between the heavy quarks is
between 50 and 80 GeV. Although heavy quarks can be easily detected at the LHC,
it is very difficult to detect a sequential heavy charged lepton, L, due to
large backgrounds. Should the L mass be above 250 GeV, it can not be
pair-produced at a 500 GeV ILC. We calculate the cross section for the one-loop
process e+e- -> L tau. Although the cross section is small, it may be
detectable. We also consider contributions from the two Higgs doublet model and
the Randall-Sundrum model, in which case the cross section can be substantially
higher.
