  We provide high-precision predictions for muon-pair and tau-pair productions
in a photon-photon collision by considering a complete set of one-loop-level
scattering amplitudes, i.e., electroweak (EW) corrections together with soft
and hard QED radiation. Accordingly, we present a detailed numerical discussion
with particular emphasis on the pure QED corrections as well as genuinely weak
corrections. The effects of angular and initial beam polarisation distributions
on production rates are also discussed. An improvement is observed by a factor
of two with oppositely polarized photons. Our results indicate that the
one-loop EW radiative corrections enhance the Born cross section and the total
relative correction is typically about ten percent for both production
channels. It appears that the full EW corrections to $\gamma \gamma \to \ell^-
\ell^+$ are required to match a percent level accuracy.
