  High-precision analyses are presented for the production of scalar sleptons,
selectrons and smuons in supersymmetric theories, at future e+e- and e-e-
linear colliders. Threshold production can be exploited for measurements of the
selectron and smuon masses, an essential ingredient for the reconstruction of
the fundamental supersymmetric theory at high scales. The production of
selectrons in the continuum will allow us to determine the Yukawa couplings in
the selectron sector, scrutinizing the identity of the Yukawa and gauge
couplings, which is a basic consequence of supersymmetry. The theoretical
predictions are elaborated at the one-loop level in the continuum, while at
threshold non-zero width effects and Sommerfeld rescattering corrections are
included. The phenomenological analyses are performed for e+e- and e-e- linear
colliders with energy up to about 1 TeV and with high integrated luminosity up
to 1 ab^-1 to cover the individual slepton channels separately with high
precision.
