  The electroweak contributions to the forward-backward asymmetry in the
production of top-quark pairs at the Tevatron are evaluated at O(alpha^2) and
O(alpha*alphas^2). We perform a detailed analysis of all partonic channels that
produce an asymmetry and combine them with the QCD contributions. They provide
a non-negligible fraction of the QCD-induced asymmetry with the same overall
sign, thus enlarging the Standard Model prediction and diminishing the observed
deviation. For the observed mass-dependent forward-backward asymmetry a 3-sigma
deviation still remains at an invariant-mass cut of M_(t-tbar) > 450 GeV.
