A new QCD analysis of deep inelastic scattering (DIS) data is presented. Al
l available neutrino and antineutrino cross sections are reanalyzed and inc
luded in the fit, along with charged-lepton DIS and Drell-Yan data. A massi
ve factorization scheme is used to describe the charm component of the stru
cture functions. Next-to-leading-order parton distribution functions are pr
ovided. In particular, the strange-sea density is determined with a higher
accuracy with respect to other global fits.