  A sizeable difference in the differential production cross section of top and
antitop quarks, respectively, is predicted for hadronically produced heavy
quarks. It is of order $\alpha_s$ and arises from the interference between
charge odd and even amplitudes respectively. For the TEVATRON it amounts up to
15\% for the differential distribution in suitable chosen kinematical regions.
The resulting integrated forward-backward asymmetry of 4--5\% could be measured
in the next round of experiments. At the LHC the asymmetry can be studied by
selecting appropriately chosen kinematical regions. Furthermore, a slight
preference at LHC for centrally produced antitop is predicted, with top quarks
more abundant at large positive and negative rapidities.
