  Using data from a recent reanalysis of neutron structure functions extracted
from inclusive proton and deuteron deep-inelastic scattering (DIS), we
re-examine the constraints on the shape of the $\bar d-\bar u$ asymmetry in the
proton at large parton momentum fractions $x$. A global analysis of the
proton-neutron structure function difference from BCDMS, NMC, SLAC and
Jefferson Lab DIS measurements, and of Fermilab Drell-Yan lepton-pair
production cross sections, suggests that existing data can be well described
with $\bar d > \bar u$ for all values of $x$ currently accessible. We compare
the shape of the fitted $\bar d-\bar u$ distributions with expectations from
nonperturbative models based on chiral symmetry breaking, which can be tested
by upcoming Drell-Yan data from the SeaQuest experiment at larger values of
$x$.
