The strong impact of longitudinally polarized electron and positron
beams on precision studies of top quark production and decay close
to the production threshold is demonstrated.
The right-left asymmetry of the production cross section
can be measured with a precision of one to two percent.
The top quarks will be highly polarized which allows to measure the
couplings responsible for the top quark decay.
As characteristic examples the decay chains top –> bottom W(–> e + neutrino and top –> Higgs + bottom will be considered.