  We discuss the possibility to study oscillations of atmospheric neutrinos in
the ATLAS experiment at CERN. Due to the large total detector mass, a
significant number of events is expected, and during the shutdown phases of the
LHC, reconstruction of these events will be possible with very good energy and
angular resolutions, and with charge identification. We argue that 500 live
days of neutrino running could be achieved, and that a total of ~160 contained
\nu_\mu events and ~360 upward going muons could be collected during this time.
Despite the low statistics, the excellent detector resolution will allow for an
unambiguous confirmation of atmospheric neutrino oscillations and for
measurements of the leading oscillation parameters. Though our detailed
simulations show that the sensitivity of ATLAS is worse than that of dedicated
neutrino experiments, we demonstrate that more sophisticated detectors, e.g. at
the ILC, could be highly competitive with upcoming superbeam experiments, and
might even give indications for the mass hierarchy and for the value of
theta-13.
