  The parton momentum density distributions in the proton are determined from a
next-to-leading order QCD analysis of structure functions measured at HERA and
by fixed target experiments. Also included are data on the difference of the up
and down anti-quark distributions. The uncertainties in the parton densities,
structure functions and related cross sections are estimated from the
experimental errors and those on the input parameters of the fit. Several QCD
predictions obtained from this analysis are calculated and compared to data.
The parton densites including the full error information is made available on a
computer readable file.
