The atmospheric neutrino charged current events rate, expected without oscillations, in one year, for a sensitive mass of about 500 t, is of about 140 events, 80 from nm and 60 from ne interactions. These rates correspond to the number of events with a vertex within this sensitive mass. Atmospheric neutrino interactions, with a mean neutrino energy of the order of few hundreds MeV, produce low multiplicity events with a lepton (m or e) accompanied by a nucleon (p or n) and possibly by one (or two) pion(s). This kind of topologies can be perfectly reconstructed with the ICARUS detector, providing a complete information on the incoming neutrino kinematics.

Therefore, the ICARUS experiment is well suited to perform, in a few years of exposure, the atmospheric neutrino study with sufficient sensitivity to cover the Super-Kamiokande allowed regions in the neutrino oscillation parameter space.