Top quark-antiquark (t tbar) pairs will be produced copiously at the
Tevatron collider and in huge numbers at the LHC. This will make possible
detailed investigations of the properties and interactions of this quark
flavor. The analysis and interpretation of future data requires precise
predictions of the hadronic production of ttbar pairs and of their
subsequent decays. In this talk the reactions
p pbar, p p –> t tbar X –> l^+l^-X are considered and results are
presented of our calculation of the dilepton angular distribution
at next-to-leading order QCD, keeping the full dependence on the spins
of the intermediate t tbar state. The angular distribution is determined
for different choices of reference axes that can be identified with the
t and tbar spin axes. While the QCD corrections to the leading-order
distribution turn out to be small in the case of the LHC, we find them
to be sizeable in the case of the Tevatron and find, moreover, the
angular distribution to be sensitive to the parton content of the proton.
