Electroweak corrections to Bs,d → l+l-

We calculate the full two-loop electroweak matching corrections to the operator governing the decay B-q -> l(+)l(-) in the standard model. Their inclusion removes an electroweak scheme and scale uncertainty of about +/- 7% of the branching ratio. Using different renormalization schemes of the involved electroweak parameters, we estimate residual perturbative electroweak and QED uncertainties to be less than +/- 1% at the level of the branching ratio.