2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/184185The ultrahigh energy neutrino cross section is reviewed. Experimental results from HERA electron-proton and positron-proton scattering have yielded new information about the small x behavior of the parton distribution functions. We compare pre-HERA era neutrino-nucleon cross sections with more recent evaluations.5 pages, 4 figures, to appear in the Proceedings of the XIII International Symposium on Very High Energy Cosmic Ray Interactions, 6-12 September 2004, Pylos, GreeceHigh Energy Physics - Phenomenologytext