  In this talk we would like to present recent calculations of the cross
sections for the ultrahigh energy neutrinos interacting with nucleons. We
briefly present the framework of unifed BFKL/DGLAP equations which resums all
the leading log(1/x) effects as well as the subleading terms. The few free
parameters which specify the input parton distributions are determined by
fitting to HERA deep inelastic data. We then use these parton distributions to
calculate the cross section for the neutrino-nucleon interactions at very high
energies, up to 10^12 GeV.
  We do also investigate the attenuation of neutrinos when traversing through
the Earth. We use the transport equation which we solve for different fluxes of
high energy neutrinos (Active Galactic Nucleai, Gamma Ray Bursts, and top-down
models). We study the effects of the regeneration of the neutrino flux via
neutral current interaction.
