  We present a new measurement of the inclusive forward-backward t-tbar
production asymmetry and its rapidity and mass dependence. The measurements are
performed with 5.3 fb^{-1} of p-pbar collisions at \sqrt{s} = 1.96 TeV,
recorded with CDF II at the Fermilab Tevatron. Significant inclusive
asymmetries are observed in the laboratory and t-tbar rest frame, and are
consistent with CP conservation under interchange of t and tbar. In the t-tbar
rest frame, the asymmetry increases with the t-tbar rapidity difference,
\Delta(y), and with the invariant mass M_{t-tbar} of the t-tbar system.
Parton-level asymmetries are derived in two regions of each variable, and the
asymmetry is found to be most significant at large \Delta(y) and M_{t-tbar}.
For M_{t-tbar} > 450 GeV/c^2, the parton-level asymmetry in the t-tbar rest
frame is A^{t-tbar} = 0.475\pm 0.114 compared to a next-to-leading order QCD
prediction of 0.088\pm 0.013.
