  We discuss the production of heavy leptons at a future high--energy $e^+e^-$
linear collider with a center of mass energy of 500 GeV. Signals and
backgrounds are analyzed for their single production in association with
ordinary leptons. [Talk given by A.D. at the second Workshop on "Physics and
Experiments with Linear e+e- Colliders", Waikoloa, Hawaii, April 1993].
