Distinctive signatures for new particles in e+e- annihilation and Z-decay

New particles and new interactions reveal themselves most clearly where standard model contributions are negligibly small. A prominent example with this advantage is the one-lepton inclusive longitudinal structure function (Wsub(L)) in e+e- annihilation and Z-decay. We discuss general features of this approach and present structure functions for two types of new particles (heavy charged fermion, e.g. new sequential lepton or top quark; and supersymmetric scalar lepton, i.e. slepton), along with the (small) standard model ''background''. The x-dependence of Wsub(L) provides a distinct signature of the identity of the new particle. Extensions of this approach are discussed. (orig.)