The asymmetry in W^- - W^+ production in ppbar collisions and
Drell-Yan data place tight constraints on parton distributions functions.
The W asymmetry data constrain the slope of the quark distribution ratio
d(x)/u(x) in the x range 0.007-0.27.  The published W asymmetry results from
the CDF 1992-3 data (\approx 20 pb^-1) greatly reduce the systematic error
originating from the choice of PDF's in the W mass measurement at CDF.  These
published results have also been included in the CTEQ3, MRSA, and GRV94 parton
distribution fits.  These modern parton distribution functions are still in
good agreement with the new 1993-94 CDF data (\approx 108 pb^-1 combined).
Preliminary results from CDF for the Drell-Yan cross section in the mass range
11-350 GeV/c^3 are discussed.