Experimental signatures of composite quarks and leptons

Certain types of composite models of quarks and leptons are expected to lead to low-lying excited states of quarks and leptons, possibly of masses as low as 20 GeV. Production cross sections of such excited states in $e^{+}{e}^{-}$ annihilation and in inelastic lepton-nucleon scattering are calculated. Questions of observability of excited but confined quarks are discussed. It appears that excited quarks and leptons can be best seen in annihilation experiments at c.m.-system energies close to the mass of the $Z^0$ boson.