  Beam polarization at e+ e- linear colliders will be a powerful tool for high
precision analyses. Often it is assumed that the full information from
polarization effects is provided by polarization of the electron beam and no
further information can be obtained by the simultaneous polarization of the
positrons. In this paper we point out the advantages of polarizing both beams,
and summarize the polarization-related results of the Higgs, Electroweak, QCD,
SUSY and Alternative Theories working groups of the ECFA/DESY workshop for a
planned linear collider operating in the energy range sqrt{s}= 500-800 GeV.
