Supersymmetry and compositeness at linear colliders

We discuss the search for supersymmetric partners of leptons, quarks and gauge bosons as well as for compositeness effects in the leptonic and bosonic sectors of the reactions e+e−→W+W−, ZZ, γZ, γγ at future e+e− linear colliders in the TeV range. Electron beam longitudinal polarization effects are included. Limits of observability on masses of supersymmetric partners and on compositeness scales are given.