  To obtain improved parton densities of the proton, we present a new global
analysis of deep inelastic and related data including, in particular, the
recent measurements of $F_2$ at HERA, of the asymmetry of the rapidity
distributions of $W^\pm$ production at the FNAL $pp$ collider and of the
asymmetry in Drell-Yan production in $pp$ and $pn$ collisions. We also
incorporate data to determine the flavour dependence of the quark sea
distributions. We find that the behaviour of the partons at small $x$ is
consistent with the precocious onset of BFKL leading $\log(1/x)$ dynamics. We
discuss the ambiguities remaining in the gluon distribution. We present
improved predictions for $W$ boson (and $t$ quark) production at the FNAL $\pp$
collider.
