  Top-antitop quark pairs belong to the most abundantly produced and precisely
measurable heavy-particle signatures at hadron colliders and allow for crucial
tests of the Standard Model and new-physics searches. Here we report on the
calculation of the next-to-leading order (NLO) QCD corrections to hadronic WWbb
production, which provides a complete NLO description of the production of
top-antitop pairs and their subsequent decay into W bosons and bottom quarks,
including interferences, off-shell effects, and non-resonant backgrounds.
Numerical predictions for the Tevatron and the LHC are presented.
