  Using the new schemes provided by the CTEQ and MRST collaborations and by
Alekhin, we analyse the uncertainties due to the parton distribution functions
(PDFs) on the next-to-leading-order cross sections of the four main production
processes of the Standard Model Higgs boson at the LHC and the Tevatron. In the
Higgs mass range where the production rates are large enough, the spread in the
uncertainties when the three sets of PDFs are compared is of about 15% in all
processes and at both colliders. However, within one given set of PDFs, the
deviations from the values obtained with the reference sets are much smaller,
being of ${\cal O}(5$%), except in the gluon--gluon fusion mechanism at
relatively large Higgs boson masses, where they can reach the level of 10%
(15%) at the LHC (Tevatron).
