  We present a three-dimensional calculation of atmospheric neutrino fluxes
using accurate models of the geomagnetic field, hadronic interactions, tracking
and decays. Results are presented for the Super-Kamiokande (SK) and Sudbury
Neutrino Observatory (SNO) sites using the GEANT-FLUKA hadronic code. We make a
comparison with previous one-dimensional calculations and other
three-dimensional results. The recently reported geometrical enhancement of low
energy, horizontal neutrinos is confirmed. The effect on observed leptons is
however, restricted to a small overall increase in flux. We report east-west
asymmetries for each of the neutrino species.
