  A detailed, model-independent study of CP violation at present and future
electron-positron colliders is reported. Firstly, we investigate CP violation
effects in $W$ boson and $t$ quark pair production in $e^+e^-$ annihilation and
in two-photon fusion at a next $e^+e^-$ linear collider, where
Compton-backscattered laser light off the electrons or positrons are employed
as a powerful polarized photon source. Secondly, noting that there do not exist
any direct measurements for the tau-lepton electric dipole moment (EDM), we
address the importance of performing its direct measurements at $e^+e^-$
collisions off the Z-boson pole at TRISTAN, LEPII and CLEOII. We present a
rough comparison of the potential of these experiments in the $\tau$ EDM
measurements. Finally, we report on our recent works for probing CP violation
in the semileptonic decays of the tau lepton, which involve two different
intermediate resonances with large ratios of widths to masses, and which can be
most efficiently identified at the planned $B$ and proposed $\tau$-charm
factories. All the CP-violation phenomena in the processes under consideration,
if discovered, imply new CP-violation mechanisms completely different from the
Standard Model CP violation mechanism through the complex phase of the
Cabibbo-Kobayashi-Maskawa matrix.
