  The cross-section for $\gamma\gamma\to t \bar t$ with arbitrary polarized
photons is calculated within the electroweak Standard Model including the
complete virtual and soft-photonic $O(\alpha)$ corrections. We present a
detailed numerical discussion of the radiative corrections with particular
emphasis on the purely weak corrections. These are usually of the order of
1--10\% for energies up to 1 TeV. For unpolarized or equally polarized photons
they reach almost 10\% close to threshold. The large corrections cannot be
traced back to a universal origin like the running of $\alpha$ or the
$\rho$-parameter. Apart from the energy region around the Higgs resonance
$(\gamma\gamma\to H^*\to t\bar t)$ the weak corrections are widely independent
of the Higgs-boson mass.
