  The investigation of lepton-hadron and photon-hadron collisions at TeV scale
is crucial both to clarify the strong interaction dynamics from nuclei to
quark-parton level and for adequate interpretation of experimental data from
future hadron colliders (LHC and VLHC). In this presentation different TeV
scale lepton-hadron and photon-hadron collider proposals (such as THERA,
LEP-LHC, QCD Explorer etc) are discussed. The advantages of linac-ring type
colliders has been shown comparatively.
