  Cross sections for the interactions of ultrahigh-energy neutrinos with
nucleons are evaluated in light of new information about nucleon structure
functions. For $10^{20}$--eV neutrinos, the cross section is about 2.4 times
previous estimates. We also review the cross sections for neutrino interactions
with atomic electrons. Some consequences for interaction rates in the Earth and
for event rates from generic astrophysical sources in large-scale detectors are
noted.
